[office/crow-translate] src: Fix Windows multi-monitor capture area with per-monitor DPI

Git commit da9ff89d35c1f2c26c2e067029b3f4e0888790c4 by Mauritius Clemens.
Committed on 16/08/2026 at 22:20.
Pushed by pillowtrucker into branch 'master'.

Fix Windows multi-monitor capture area with per-monitor DPI

Request PER_MONITOR_AWARE_V2 so Qt reports consistent geometry across a
scaled main monitor and a second monitor. Map the capture selection from the
overlay's logical coordinates into device pixels per-screen in
SnippingArea::selectedPixmap, so the grabbed image is correctly offset and
scaled for OCR on 200%-scaled or mixed-DPI setups.

M  +12   -0    src/main.cpp
M  +52   -4    src/ocr/snippingarea.cpp
M  +4    -0    src/ocr/snippingarea.h

https://invent.kde.org/office/crow-translate/-/commit/da9ff89d35c1f2c26c2e067029b3f4e0888790c4

diff --git a/src/main.cpp b/src/main.cpp
index ab9c57a3..f892e1d8 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -18,6 +18,12 @@
 #include <KIconTheme>
 #endif
 
+#ifdef Q_OS_WIN
+#define WIN32_LEAN_AND_MEAN
+#define NOMINMAX
+#include <windows.h>
+#endif
+
 #ifdef Q_OS_UNIX
 #include "ocr/ocr.h"
 
@@ -69,6 +75,12 @@ int launchGui(int argc, char *argv[])
 
 #if defined(Q_OS_WIN)
     QGuiApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);
+    // Request per-monitor DPI awareness (V2) explicitly so that the screen
+    // geometry and grabbed images reported by Qt use a single, consistent scale
+    // regardless of any application manifest. Without this, on a scaled main
+    // monitor alongside a second monitor the capture area maps its coordinates
+    // incorrectly and the grabbed pixmap is offset or clipped.
+    SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
 #endif
 #if defined(Q_OS_LINUX)
     QGuiApplication::setDesktopFileName(QStringLiteral(DESKTOP_FILE_BASENAME));
diff --git a/src/ocr/snippingarea.cpp b/src/ocr/snippingarea.cpp
index 9ae3a789..a2dd324c 100644
--- a/src/ocr/snippingarea.cpp
+++ b/src/ocr/snippingarea.cpp
@@ -449,7 +449,7 @@ int SnippingArea::boundsLeft(int newTopLeftX, bool mouse)
 int SnippingArea::boundsRight(int newTopLeftX, bool mouse)
 {
     // The max X coordinate of the top left point
-    const int realMaxX = qRound((width() - m_selection.width()) * devicePixelRatioF());
+    const int realMaxX = width() - m_selection.width();
     const int xOffset = newTopLeftX - realMaxX;
     if (xOffset > 0) {
         if (mouse)
@@ -763,16 +763,62 @@ SnippingArea::MouseState SnippingArea::mouseLocation(QPointF pos) const
 
 QPixmap SnippingArea::selectedPixmap() const
 {
-    return m_screenPixmap.copy(m_selection);
+    // The selection is stored in the overlay's logical (device-independent)
+    // coordinates, but each screen image is captured at its native
+    // (device-pixel) resolution. Extract the selection at full resolution by
+    // intersecting it with every screen and scaling by that screen's
+    // devicePixelRatio, preserving the pixels for OCR.
+    const QRect deviceSelection = toDeviceRect(m_selection);
+    QPixmap result(deviceSelection.size());
+    result.fill(Qt::transparent);
+
+    QPainter painter(&result);
+    for (auto it = m_images.constBegin(); it != m_images.constEnd(); ++it) {
+        const QRect screenArea = deviceGeometry(it.key()).translated(-m_deviceScreensRect.topLeft());
+        const QRect matched = screenArea.intersected(deviceSelection);
+        if (matched.isEmpty())
+            continue;
+
+        const QRect sourceRect = matched.translated(-screenArea.topLeft());
+        painter.drawImage(matched.translated(-deviceSelection.topLeft()), it.value(), sourceRect);
+    }
+    return result;
+}
+
+QRect SnippingArea::deviceGeometry(const QScreen *screen)
+{
+    const qreal dpr = screen->devicePixelRatio();
+    const QRect geometry = screen->geometry();
+    return QRect(qRound(geometry.x() * dpr),
+                 qRound(geometry.y() * dpr),
+                 qRound(geometry.width() * dpr),
+                 qRound(geometry.height() * dpr));
+}
+
+QRect SnippingArea::toDeviceRect(const QRect &rect) const
+{
+    // Map a rectangle expressed in the overlay's logical coordinates to the
+    // device-pixel space of the composited screenshot. Use the screen under the
+    // rectangle's center so that a single consistent scale factor is applied.
+    const QPointF overlayCenter = rect.center() + m_screensRect.topLeft();
+    const QScreen *screen = QGuiApplication::screenAt(overlayCenter.toPoint());
+    if (screen == nullptr)
+        screen = QGuiApplication::primaryScreen();
+
+    const qreal dpr = screen->devicePixelRatio();
+    const QPointF screenRelativeTopLeft = rect.topLeft() + m_screensRect.topLeft() - screen->geometry().topLeft();
+    const QPointF deviceTopLeft = screenRelativeTopLeft * dpr + deviceGeometry(screen).topLeft() - m_deviceScreensRect.topLeft();
+    return QRect(deviceTopLeft.toPoint(), QSizeF(rect.width() * dpr, rect.height() * dpr).toSize());
 }
 
 void SnippingArea::createPixmapFromScreens()
 {
-    m_screenPixmap = QPixmap(m_screensRect.width(), m_screensRect.height());
+    m_screenPixmap = QPixmap(m_screensRect.size());
     QPainter painter(&m_screenPixmap);
     // Geometry can have negative coordinates, so it is necessary to subtract the upper left point, because coordinates on the widget are counted from 0
+    // Each screen image is grabbed at its native resolution, so it must be scaled down to the screen's logical geometry when composited
     for (auto it = m_images.constBegin(); it != m_images.constEnd(); ++it)
-        painter.drawImage(it.key()->geometry().topLeft() - m_screensRect.topLeft(), it.value());
+        painter.drawImage(it.key()->geometry().translated(-m_screensRect.topLeft()), it.value());
 }
 
 void SnippingArea::setGeometryToScreenPixmap()
@@ -880,8 +926,10 @@ void SnippingArea::setBottomHelpText()
 void SnippingArea::preparePaint()
 {
     m_screensRect = {};
+    m_deviceScreensRect = {};
     for (auto it = m_images.constBegin(); it != m_images.constEnd(); ++it) {
         m_screensRect = m_screensRect.united(it.key()->geometry());
+        m_deviceScreensRect = m_deviceScreensRect.united(deviceGeometry(it.key()));
     }
 }
 
diff --git a/src/ocr/snippingarea.h b/src/ocr/snippingarea.h
index daaa153c..ccc491bf 100644
--- a/src/ocr/snippingarea.h
+++ b/src/ocr/snippingarea.h
@@ -104,6 +104,9 @@ private:
     static bool isPointInsideCircle(QPointF circleCenter, qreal radius, QPointF point);
     static bool isInRange(qreal low, qreal high, qreal value);
     static bool isWithinThreshold(qreal offset, qreal threshold);
+    static QRect deviceGeometry(const QScreen *screen);
+
+    QRect toDeviceRect(const QRect &rect) const;
 
     static constexpr int s_handleRadiusMouse = 9;
     static constexpr int s_handleRadiusTouch = 12;
@@ -146,6 +149,7 @@ private:
     QPointF m_startPos;
     QPointF m_initialTopLeft;
     QRect m_screensRect;
+    QRect m_deviceScreensRect;
 
     QMap<const QScreen *, QImage> m_images;