Assume GPUs on non-x86 platforms are slow by default

This can be overriden with GL_IS_SLOW=0 at runtime
for systems with a fast GPU, though it doesn't make
much difference either way for non-KMSDRM cases.

For slower GPUs, this enables important scaling and
rendering optimizations that can substantially
improve performance (especially on fillrate-limited
GPUs common in SBCs).

app/streaming/video/ffmpeg.cpp

@@ -344,7 +344,7 @@ bool FFmpegVideoDecoder::createFrontendRenderer(PDECODER_PARAMETERS params, bool
 #ifdef GL_IS_SLOW
         glIsSlow = true;
 #else
-        glIsSlow = false;
+        glIsSlow = WMUtils::isGpuSlow();
 #endif
     }
 
@@ -352,7 +352,7 @@ bool FFmpegVideoDecoder::createFrontendRenderer(PDECODER_PARAMETERS params, bool
 #ifdef VULKAN_IS_SLOW
         vulkanIsSlow = true;
 #else
-        vulkanIsSlow = false;
+        vulkanIsSlow = WMUtils::isGpuSlow();
 #endif
     }
 
@@ -1298,7 +1298,7 @@ bool FFmpegVideoDecoder::tryInitializeRendererForUnknownDecoder(const AVCodec* d
 #ifdef GL_IS_SLOW
         glIsSlow = true;
 #else
-        glIsSlow = false;
+        glIsSlow = WMUtils::isGpuSlow();
 #endif
     }
 
@@ -1306,7 +1306,7 @@ bool FFmpegVideoDecoder::tryInitializeRendererForUnknownDecoder(const AVCodec* d
 #ifdef VULKAN_IS_SLOW
         vulkanIsSlow = true;
 #else
-        vulkanIsSlow = false;
+        vulkanIsSlow = WMUtils::isGpuSlow();
 #endif
     }
 

app/wm.cpp

@@ -210,7 +210,8 @@ bool WMUtils::isGpuSlow()
     bool ret;
 
     if (!Utils::getEnvironmentVariableOverride("GL_IS_SLOW", &ret)) {
-#ifdef GL_IS_SLOW
+#if defined(GL_IS_SLOW) || !defined(Q_PROCESSOR_X86)
+        // We currently assume GPUs on non-x86 hardware are slow by default
         ret = true;
 #else
         ret = false;