new cairo image example
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Stefan Salewski
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176
README.adoc
176
README.adoc
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@ -1640,5 +1640,181 @@ proc main =
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main()
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main()
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----
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----
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== One more cairo example
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Recently Mr. C. Eric Cashon provided an example code for working with a large bitmap image.
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His example writes the image to disk, loads it again and displays the image allowing
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zooming and translation. As examples are rare in these days, and that example is not to large,
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I used c2nim to convert it to Nim. Below is the code with a few manually fixes. Note, the
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current shipped cairo.nim module contains an assert statement, which prevents running this example.
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If you really intent running this code, you will have to fix that single line in cairo.nim. I
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have to do some more fixes in the cairo module and may ship a new version eventually. This
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example is really low level, as alloc() is used directly.
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[[cairoImage.nim]]
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[source,nim]
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.cairoImage.nim
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----
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# https://discourse.gnome.org/t/proper-zoom-pan-image-approach-for-large-images/1497/6
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# Nim version of the C example of C. Eric Cashon
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import gintro/[gtk, gobject, glib, cairo]
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from math import TAU
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import strutils
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const
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Width = 5000
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Height = 5000
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CFormat = cairo.Format.argb32
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var
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Key: cairo.UserDataKey
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translateX: float
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translateY: float
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scale = 1.0
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## Store data from file.
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bigSurfaceData*: ptr cuchar = nil
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proc translateXSpinChanged(spinButton: SpinButton; data: DrawingArea) =
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translateX = spinButton.value
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data.queueDraw
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proc translateYSpinChanged(spinButton: SpinButton; data: DrawingArea) =
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translateY = spinButton.getValue
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data.queueDraw
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proc scaleSpinChanged(spinButton: SpinButton; data: DrawingArea) =
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scale = spinButton.value
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data.queueDraw
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proc saveBigSurface =
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## Use gdk_cairo_surface_create_from_pixbuf() to read in a pixbuf. Try a test surface here.
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let bigSurface = imageSurfaceCreate(CFormat, Width, Height)
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let cr = newContext(bigSurface)
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## Paint the background.
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cr.setSource(1, 1, 1)
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cr.paint
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## Draw a circle.
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cr.setSource(0, 0, 1)
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cr.arc(250, 250, 50, 0, math.TAU)
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cr.fill
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## Draw some test grid lines.
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cr.setSource(0, 1, 0)
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for i in countup(0, 4900, 100):
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cr.moveTo(0, i.float)
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cr.lineTo(5000, i.float)
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cr.stroke
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for i in countup(0, 4900, 100):
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cr.moveTo(i.float, 0)
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cr.lineTo(i.float, 5000)
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cr.stroke
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cr.setSource(0, 0, 1)
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cr.setLineWidth(10)
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for i in 0 ..< 10:
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cr.moveTo(0, i.float * 500.0)
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cr.lineTo(5000, i.float * 500.0)
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cr.stroke
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for i in 0 ..< 10:
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cr.moveTo(i.float * 500.0, 0)
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cr.lineTo(i.float * 500.0, 5000)
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cr.stroke
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## Outside box.
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cr.setLineWidth(20)
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cr.setSource(1, 0, 1)
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cr.rectangle(0, 0, 5000, 5000)
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cr.stroke
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## Save surface data to file.
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let f: File = open("big_surface.s", fmWrite)
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let p: ptr cuchar = cairo_image_surface_get_data(bigSurface.impl)
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let len = writeBuffer(f, p, cairo_format_stride_for_width(CFormat, Width) * Height)
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echo("write $1\n" % $len)
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close(f)
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proc myDealloc(data: pointer) {.cdecl.} =
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system.dealloc(data)
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proc getBigSurface(): Surface =
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let f: File = open("big_surface.s", fmRead)
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# setFilePos(f, 0)
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# https://www.cairographics.org/manual/cairo-Image-Surfaces.html#cairo-format-stride-for-width
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let stride = cairo_format_stride_for_width(CFormat, Width)
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bigSurfaceData = cast[ptr cuchar](malloc((stride * Height).uint64))
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var len = readBuffer(f, bigSurfaceData, stride * Height)
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echo("read $1" % $len)
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close(f)
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let bigSurface: Surface = new Surface # this is a temporary fix, we will support this later in cairo modul
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bigSurface.impl = cairo_image_surface_create_for_data(bigSurfaceData, CFormat, Width, Height, stride)
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discard setUserData(bigSurface, addr(Key), bigSurfaceData, myDealloc) # automatic deallocation
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# flush(bigSurface)
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echo("open $1" % bigSurface.status.statusToString)
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return bigSurface
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proc daDrawing*(da: DrawingArea; cr: Context; bigSurface: Surface): bool =
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var
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width = da.getAllocatedWidth.float
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height = da.getAllocatedHeight.float
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originX = translateX
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originY = translateY
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## Some constraints.
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if translateX > 5000.0 - width:
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originX = 5000.0 - width / scale
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if translateY > 5000.0 - height:
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originY = 5000.0 - height / scale
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cr.setSource(0, 0, 0)
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cr.paint
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## Partition the big surface.
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var littleSurface: Surface = cairo.surfaceCreateForRectangle(bigSurface,
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originX, originY, width / scale, height / scale)
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cr.scale(scale, scale)
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cr.setSourceSurface(littleSurface, 0, 0)
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setFilter(getSource(cr), cairo.Filter.bilinear)
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cr.paint
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return true
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proc bye(w: Window) =
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mainQuit()
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echo "Bye..."
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proc main =
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gtk.init()
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let window = newWindow()
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window.setTitle("Big Surface2")
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window.setDefaultSize(500, 500)
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window.setPosition(gtk.WindowPosition.center)
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window.connect("destroy", bye)
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## Get a test surface.
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saveBigSurface()
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let bigSurface = getBigSurface()
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let da: DrawingArea = newDrawingArea()
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da.setHexpand
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da.setVexpand
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da.connect("draw", daDrawing, bigSurface)
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let
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translateXAdj = newAdjustment(0, 0, 5000, 20, 0, 0)
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translateYAdj = newAdjustment(0, 0, 5000, 20, 0, 0)
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scaleAdj = newAdjustment(1, 1, 5, 0.1, 0, 0)
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translateXLabel = newLabel("translate x")
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translateXSpin= newSpinButton(translateXAdj, 50, 1)
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connect(translateXSpin, "value-changed", translateXSpinChanged, da)
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let translateYLabel = newLabel("translate y")
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let translateYSpin = newSpinButton(translateYAdj, 50, 1)
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connect(translateYSpin, "value-changed", translateYSpinChanged, da)
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let scaleLabel = newLabel("Scale")
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let scaleSpin = newSpinButton(scaleAdj, 0.2, 1)
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connect(scaleSpin, "value-changed", scaleSpinChanged, da)
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let grid = newGrid()
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grid.attach(da, 0, 0, 3, 1)
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grid.attach(translateXLabel, 0, 1, 1, 1)
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grid.attach(translateYLabel, 1, 1, 1, 1)
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grid.attach(scaleLabel, 2, 1, 1, 1)
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grid.attach(translateXSpin, 0, 2, 1, 1)
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grid.attach(translateYSpin, 1, 2, 1, 1)
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grid.attach(scaleSpin, 2, 2, 1, 1)
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add(window, grid)
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showAll(window)
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gtk.main()
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main()
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----
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NOTE: Related work: https://github.com/jdmansour/nim-smartgi
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NOTE: Related work: https://github.com/jdmansour/nim-smartgi
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160
examples/gtk3/cairoImage.nim
Normal file
160
examples/gtk3/cairoImage.nim
Normal file
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@ -0,0 +1,160 @@
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# https://discourse.gnome.org/t/proper-zoom-pan-image-approach-for-large-images/1497/6
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# Nim version of the C example of C. Eric Cashon
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import gintro/[gtk, gobject, glib, cairo]
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from math import TAU
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import strutils
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const
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Width = 5000
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Height = 5000
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CFormat = cairo.Format.argb32
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var
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Key: cairo.UserDataKey
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translateX: float
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translateY: float
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scale = 1.0
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## Store data from file.
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bigSurfaceData*: ptr cuchar = nil
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proc translateXSpinChanged(spinButton: SpinButton; data: DrawingArea) =
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translateX = spinButton.value
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data.queueDraw
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proc translateYSpinChanged(spinButton: SpinButton; data: DrawingArea) =
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translateY = spinButton.getValue
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data.queueDraw
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proc scaleSpinChanged(spinButton: SpinButton; data: DrawingArea) =
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scale = spinButton.value
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data.queueDraw
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proc saveBigSurface =
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## Use gdk_cairo_surface_create_from_pixbuf() to read in a pixbuf. Try a test surface here.
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let bigSurface = imageSurfaceCreate(CFormat, Width, Height)
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let cr = newContext(bigSurface)
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## Paint the background.
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cr.setSource(1, 1, 1)
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cr.paint
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## Draw a circle.
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cr.setSource(0, 0, 1)
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cr.arc(250, 250, 50, 0, math.TAU)
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cr.fill
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## Draw some test grid lines.
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cr.setSource(0, 1, 0)
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for i in countup(0, 4900, 100):
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cr.moveTo(0, i.float)
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cr.lineTo(5000, i.float)
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cr.stroke
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for i in countup(0, 4900, 100):
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cr.moveTo(i.float, 0)
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cr.lineTo(i.float, 5000)
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cr.stroke
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cr.setSource(0, 0, 1)
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cr.setLineWidth(10)
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for i in 0 ..< 10:
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cr.moveTo(0, i.float * 500.0)
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cr.lineTo(5000, i.float * 500.0)
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cr.stroke
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for i in 0 ..< 10:
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cr.moveTo(i.float * 500.0, 0)
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cr.lineTo(i.float * 500.0, 5000)
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cr.stroke
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## Outside box.
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cr.setLineWidth(20)
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cr.setSource(1, 0, 1)
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cr.rectangle(0, 0, 5000, 5000)
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cr.stroke
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## Save surface data to file.
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let f: File = open("big_surface.s", fmWrite)
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let p: ptr cuchar = cairo_image_surface_get_data(bigSurface.impl)
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let len = writeBuffer(f, p, cairo_format_stride_for_width(CFormat, Width) * Height)
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echo("write $1\n" % $len)
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close(f)
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proc myDealloc(data: pointer) {.cdecl.} =
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system.dealloc(data)
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proc getBigSurface(): Surface =
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let f: File = open("big_surface.s", fmRead)
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# setFilePos(f, 0)
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# https://www.cairographics.org/manual/cairo-Image-Surfaces.html#cairo-format-stride-for-width
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let stride = cairo_format_stride_for_width(CFormat, Width)
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bigSurfaceData = cast[ptr cuchar](malloc((stride * Height).uint64))
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var len = readBuffer(f, bigSurfaceData, stride * Height)
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echo("read $1" % $len)
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close(f)
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let bigSurface: Surface = new Surface # this is a temporary fix, we will support this later in cairo modul
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bigSurface.impl = cairo_image_surface_create_for_data(bigSurfaceData, CFormat, Width, Height, stride)
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discard setUserData(bigSurface, addr(Key), bigSurfaceData, myDealloc) # automatic deallocation
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# flush(bigSurface)
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echo("open $1" % bigSurface.status.statusToString)
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return bigSurface
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proc daDrawing*(da: DrawingArea; cr: Context; bigSurface: Surface): bool =
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var
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width = da.getAllocatedWidth.float
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height = da.getAllocatedHeight.float
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originX = translateX
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originY = translateY
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## Some constraints.
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if translateX > 5000.0 - width:
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originX = 5000.0 - width / scale
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if translateY > 5000.0 - height:
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originY = 5000.0 - height / scale
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cr.setSource(0, 0, 0)
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cr.paint
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## Partition the big surface.
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var littleSurface: Surface = cairo.surfaceCreateForRectangle(bigSurface,
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originX, originY, width / scale, height / scale)
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cr.scale(scale, scale)
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cr.setSourceSurface(littleSurface, 0, 0)
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setFilter(getSource(cr), cairo.Filter.bilinear)
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cr.paint
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return true
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proc bye(w: Window) =
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mainQuit()
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echo "Bye..."
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proc main =
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gtk.init()
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let window = newWindow()
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window.setTitle("Big Surface2")
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window.setDefaultSize(500, 500)
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window.setPosition(gtk.WindowPosition.center)
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window.connect("destroy", bye)
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## Get a test surface.
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saveBigSurface()
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let bigSurface = getBigSurface()
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let da: DrawingArea = newDrawingArea()
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da.setHexpand
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da.setVexpand
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da.connect("draw", daDrawing, bigSurface)
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let
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translateXAdj = newAdjustment(0, 0, 5000, 20, 0, 0)
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translateYAdj = newAdjustment(0, 0, 5000, 20, 0, 0)
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scaleAdj = newAdjustment(1, 1, 5, 0.1, 0, 0)
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translateXLabel = newLabel("translate x")
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translateXSpin= newSpinButton(translateXAdj, 50, 1)
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connect(translateXSpin, "value-changed", translateXSpinChanged, da)
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let translateYLabel = newLabel("translate y")
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let translateYSpin = newSpinButton(translateYAdj, 50, 1)
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connect(translateYSpin, "value-changed", translateYSpinChanged, da)
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let scaleLabel = newLabel("Scale")
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let scaleSpin = newSpinButton(scaleAdj, 0.2, 1)
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connect(scaleSpin, "value-changed", scaleSpinChanged, da)
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let grid = newGrid()
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grid.attach(da, 0, 0, 3, 1)
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grid.attach(translateXLabel, 0, 1, 1, 1)
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grid.attach(translateYLabel, 1, 1, 1, 1)
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grid.attach(scaleLabel, 2, 1, 1, 1)
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grid.attach(translateXSpin, 0, 2, 1, 1)
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grid.attach(translateYSpin, 1, 2, 1, 1)
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grid.attach(scaleSpin, 2, 2, 1, 1)
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add(window, grid)
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showAll(window)
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gtk.main()
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main()
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