plugins/screencast, screenshot: switch color transforms to relative colorimetric

This is to disable tone mapping, which makes screenshots of SDR things while HDR is enabled on a
display look a lot worse.
As the tradeoff, this will make HDR content look worse, but that can be fixed later by taking the
actual HDR metadata into account.

BUG: 496185

src/plugins/screencast/outputscreencastsource.cpp

@@ -72,7 +72,7 @@ void OutputScreenCastSource::render(GLFramebuffer *target)
     projectionMatrix.scale(1, -1);
     projectionMatrix.ortho(QRect(QPoint(), textureSize()));
     shaderBinder.shader()->setUniform(GLShader::Mat4Uniform::ModelViewProjectionMatrix, projectionMatrix);
-    shaderBinder.shader()->setColorspaceUniforms(colorDescription, ColorDescription::sRGB, RenderingIntent::Perceptual);
+    shaderBinder.shader()->setColorspaceUniforms(colorDescription, ColorDescription::sRGB, RenderingIntent::RelativeColorimetricWithBPC);
 
     GLFramebuffer::pushFramebuffer(target);
     outputTexture->render(textureSize());

src/plugins/screencast/regionscreencastsource.cpp

@@ -107,7 +107,7 @@ void RegionScreenCastSource::blit(Output *output)
         projectionMatrix.translate(outputGeometry.left(), outputGeometry.top());
 
         shaderBinder.shader()->setUniform(GLShader::Mat4Uniform::ModelViewProjectionMatrix, projectionMatrix);
-        shaderBinder.shader()->setColorspaceUniforms(colorDescription, ColorDescription::sRGB, RenderingIntent::Perceptual);
+        shaderBinder.shader()->setColorspaceUniforms(colorDescription, ColorDescription::sRGB, RenderingIntent::RelativeColorimetricWithBPC);
 
         outputTexture->render(outputGeometry.size());
         GLFramebuffer::popFramebuffer();

src/plugins/screenshot/screenshot.cpp

@@ -385,7 +385,7 @@ QImage ScreenShotEffect::blitScreenshot(const RenderTarget &renderTarget, const
         if (renderTarget.texture()) {
             GLFramebuffer::pushFramebuffer(&target);
             ShaderBinder binder(ShaderTrait::MapTexture | ShaderTrait::TransformColorspace);
-            binder.shader()->setColorspaceUniforms(renderTarget.colorDescription(), ColorDescription::sRGB, RenderingIntent::Perceptual);
+            binder.shader()->setColorspaceUniforms(renderTarget.colorDescription(), ColorDescription::sRGB, RenderingIntent::RelativeColorimetricWithBPC);
             QMatrix4x4 projectionMatrix;
             projectionMatrix.scale(1, -1);
             projectionMatrix *= renderTarget.transform().toMatrix();