From 2b88fab8c1a196c97851b81fd21e217f858028da Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Fri, 28 May 2021 17:33:26 +0300
Subject: [PATCH] effects/screenshot: Add support for HiDPI window screenshots

In general, on Wayland, there is no such a thing as "window scale factor"
because sub-surfaces can have different buffer scales. However, we know
the scale factor of the output where the window is considered to be on. So
we can use the screen's scale factor as the window's scale factor. In
most cases, it will produce the correct result.
---
 src/effects/screenshot/screenshot.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/effects/screenshot/screenshot.cpp b/src/effects/screenshot/screenshot.cpp
index ee6d985c5f..658b327640 100644
--- a/src/effects/screenshot/screenshot.cpp
+++ b/src/effects/screenshot/screenshot.cpp
@@ -239,14 +239,20 @@ void ScreenShotEffect::takeScreenShot(ScreenShotWindowData *screenshot)
 
     WindowPaintData d(window);
     QRect geometry = window->expandedGeometry();
+    qreal devicePixelRatio = 1;
     if (window->hasDecoration() && !(screenshot->flags & ScreenShotIncludeDecoration)) {
         geometry = window->clientGeometry();
     }
+    if (screenshot->flags & ScreenShotNativeResolution) {
+        if (const EffectScreen *screen = effects->findScreen(window->screen())) {
+            devicePixelRatio = screen->devicePixelRatio();
+        }
+    }
     bool validTarget = true;
     QScopedPointer<GLTexture> offscreenTexture;
     QScopedPointer<GLRenderTarget> target;
     if (effects->isOpenGLCompositing()) {
-        offscreenTexture.reset(new GLTexture(GL_RGBA8, geometry.size()));
+        offscreenTexture.reset(new GLTexture(GL_RGBA8, geometry.size() * devicePixelRatio));
         offscreenTexture->setFilter(GL_LINEAR);
         offscreenTexture->setWrapMode(GL_CLAMP_TO_EDGE);
         target.reset(new GLRenderTarget(*offscreenTexture));
@@ -273,6 +279,7 @@ void ScreenShotEffect::takeScreenShot(ScreenShotWindowData *screenshot)
 
             // copy content from framebuffer into image
             img = QImage(offscreenTexture->size(), QImage::Format_ARGB32);
+            img.setDevicePixelRatio(devicePixelRatio);
             glReadnPixels(0, 0, img.width(), img.height(), GL_RGBA, GL_UNSIGNED_BYTE, img.sizeInBytes(),
                           static_cast<GLvoid *>(img.bits()));
             GLRenderTarget::popRenderTarget();