From c8eeefbd7ddb6724c7b2ea8ec282046edd8e74c7 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Sun, 25 Oct 2020 17:19:07 +0200
Subject: [PATCH] platform/drm: Fix clipped HiDPI hardware cursors

If an output is rotated, we will compute a transform matrix for the
cursor plane to rotate its contents.

In order to compute that matrix we need the rect of the cursor in the
device-independent pixels, the scale factor and the output transform.

The problem is that we provide a rect of the cursor in the native
pixels. This may result in the cursor being partially or fully clipped.

CCBUG: 424589
---
 cursor.cpp                             | 5 +++++
 cursor.h                               | 1 +
 plugins/platforms/drm/drm_output.cpp   | 7 ++++---
 plugins/scenes/opengl/scene_opengl.cpp | 3 +--
 4 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/cursor.cpp b/cursor.cpp
index bb9555f259..7686d2ce92 100644
--- a/cursor.cpp
+++ b/cursor.cpp
@@ -147,6 +147,11 @@ QRect Cursor::geometry() const
     return QRect(m_pos - hotspot(), image().size());
 }
 
+QRect Cursor::rect() const
+{
+    return QRect(QPoint(0, 0), image().size() / image().devicePixelRatio());
+}
+
 QPoint Cursor::pos()
 {
     doGetPos();
diff --git a/cursor.h b/cursor.h
index 883cb540d6..da707631db 100644
--- a/cursor.h
+++ b/cursor.h
@@ -163,6 +163,7 @@ public:
     QImage image() const { return m_image; }
     QPoint hotspot() const { return m_hotspot; }
     QRect geometry() const;
+    QRect rect() const;
 
     void updateCursor(const QImage &image, const QPoint &hotspot);
     void markAsRendered() {
diff --git a/plugins/platforms/drm/drm_output.cpp b/plugins/platforms/drm/drm_output.cpp
index 3f680f8248..9d2e50d5d7 100644
--- a/plugins/platforms/drm/drm_output.cpp
+++ b/plugins/platforms/drm/drm_output.cpp
@@ -136,7 +136,8 @@ void DrmOutput::updateCursor()
     if (m_deleted) {
         return;
     }
-    QImage cursorImage = Cursors::self()->currentCursor()->image();
+    const Cursor *cursor = Cursors::self()->currentCursor();
+    const QImage cursorImage = cursor->image();
     if (cursorImage.isNull()) {
         return;
     }
@@ -146,14 +147,14 @@ void DrmOutput::updateCursor()
 
     QPainter p;
     p.begin(c);
-    p.setWorldTransform(logicalToNativeMatrix(cursorImage.rect(), scale(), transform()).toTransform());
+    p.setWorldTransform(logicalToNativeMatrix(cursor->rect(), scale(), transform()).toTransform());
     p.drawImage(QPoint(0, 0), cursorImage);
     p.end();
 }
 
 void DrmOutput::moveCursor(Cursor *cursor, const QPoint &globalPos)
 {
-    const QMatrix4x4 hotspotMatrix = logicalToNativeMatrix(cursor->image().rect(), scale(), transform());
+    const QMatrix4x4 hotspotMatrix = logicalToNativeMatrix(cursor->rect(), scale(), transform());
     const QMatrix4x4 monitorMatrix = logicalToNativeMatrix(geometry(), scale(), transform());
 
     QPoint pos = monitorMatrix.map(globalPos);
diff --git a/plugins/scenes/opengl/scene_opengl.cpp b/plugins/scenes/opengl/scene_opengl.cpp
index 77ae267106..bb4650377d 100644
--- a/plugins/scenes/opengl/scene_opengl.cpp
+++ b/plugins/scenes/opengl/scene_opengl.cpp
@@ -568,8 +568,7 @@ void SceneOpenGL2::paintCursor(const QRegion &rendered)
 
     // figure out which part of the cursor needs to be repainted
     const QPoint cursorPos = cursor->pos() - cursor->hotspot();
-    const qreal scale = cursor->image().devicePixelRatio();
-    const QRect cursorRect(QPoint(0, 0), cursor->image().size() / scale);
+    const QRect cursorRect = cursor->rect();
     QRegion region;
     for (const QRect &rect : rendered) {
         region |= rect.translated(-cursorPos).intersected(cursorRect);