fix: Implement X11 screenshot workaround for Qt6

- Added a workaround using XGetImage for capturing screenshots in X11 environments with Qt6 to address issues with QScreen::grabWindow under high DPI settings.
- Updated ScreenGrabber class to include conditional compilation for X11 support and integrated the new screenshot method.
- Modified main application logic to disable high DPI scaling when using the X11 workaround, ensuring consistent behavior across different display setups.

This update improves screenshot reliability in multi-screen and high DPI scenarios on X11.

bug: https://pms.uniontech.com/bug-view-342909.html

Author: dengzhongyuan365-dev

.gitignore

@@ -6,7 +6,8 @@ build/
 *.qm
 *.pro.user*
 
-# AI config
+AI config
 .cursor/
 .cursorindexingignore
-.specstory/
+.specstory/
+x11_paint_demo/

src/main.cpp

@@ -28,6 +28,9 @@
 #include <QFile>
 #include <QDir>
 #include <QStandardPaths>
+#if (QT_VERSION >= QT_VERSION_CHECK(6,0,0)) &&  defined(QT_QPA_PLATFORM_XCB)
+#define USE_X11_GETIMAGE 1
+#endif
 
 DWIDGET_USE_NAMESPACE
 
@@ -131,8 +134,18 @@ int main(int argc, char *argv[])
     qCDebug(dsrApp) << "Qt5: Inactive color group disabled.";
 #endif
 
+#ifdef USE_X11_GETIMAGE
+    // Qt6 X11 workaround: 禁用高 DPI 缩放
+    // Qt6 的 QScreen::grabWindow 在多屏+高DPI+非对齐布局的 X11 环境下存在 bug
+    // 禁用 DPI 缩放后，坐标系和 Qt5 一致，配合 XGetImage 可以正常工作
+    if (!isWaylandProtocol()) {
+        qputenv("QT_ENABLE_HIGHDPI_SCALING", "0");
+        qCDebug(dsrApp) << "Qt6 X11: High DPI scaling disabled (workaround for grabWindow bug).";
+    }
+#else
     QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
     qCDebug(dsrApp) << "High DPI scaling enabled.";
+#endif
 
     // 平板模式
     // Utils::isTabletEnvironment = DGuiApplicationHelper::isTabletEnvironment();

src/utils/screengrabber.cpp

@@ -15,9 +15,16 @@
 #include <QScreen>
 #include <QGuiApplication>
 #include <QPainter>
+#include <QImage>
 #include <algorithm>
 #include <QMap>
 
+// X11 headers for XGetImage workaround
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+#endif
+
 ScreenGrabber::ScreenGrabber(QObject *parent) : QObject(parent)
 {
     qCDebug(dsrApp) << "ScreenGrabber initialized.";
@@ -103,6 +110,14 @@ QPixmap ScreenGrabber::grabWaylandScreenshot(bool &ok, const QRect &rect, const
 QPixmap ScreenGrabber::grabX11Screenshot(bool &ok, const QRect &rect, const qreal devicePixelRatio)
 {
     qCDebug(dsrApp) << "Grabbing X11 screenshot for rect:" << rect;
+
+#ifdef USE_X11_GETIMAGE
+    // Qt6 workaround: 使用 XGetImage 直接抓取 X11 根窗口
+    // Qt6 的 QScreen::grabWindow 在多屏+高DPI+非对齐布局下存在 bug
+    qCDebug(dsrApp) << "Qt6: Using XGetImage workaround for X11 screenshot";
+    return grabWithXGetImage(ok, rect);
+#else
+    // Qt5: 使用原有逻辑
     const QList<QScreen*> intersectingScreens = findIntersectingScreens(rect);
 
     if (intersectingScreens.isEmpty()) {
@@ -117,6 +132,7 @@ QPixmap ScreenGrabber::grabX11Screenshot(bool &ok, const QRect &rect, const qrea
 
     qCDebug(dsrApp) << "Multiple intersecting screens found, grabbing multiple screens.";
     return grabMultipleScreens(ok, rect, intersectingScreens, devicePixelRatio);
+#endif
 }
 
 /**
@@ -538,3 +554,85 @@ QPixmap ScreenGrabber::grabMultipleScreens(bool &ok, const QRect &rect, const QL
     ok = true;
     return result;
 }
+
+#ifdef USE_X11_GETIMAGE
+/**
+ * @brief Qt6 workaround: 使用 XGetImage 直接抓取 X11 根窗口
+ * @param ok Output parameter indicating screenshot success
+ * @param rect The rectangular area to capture (in physical coordinates, since DPI scaling is disabled)
+ * @return The captured desktop image
+ * 
+ * Qt6 的 QScreen::grabWindow 在多屏+高DPI+非对齐布局的 X11 环境下存在 bug，
+ * 返回的整屏截图是花屏/错乱的。此方法绕过 Qt6 的抓图 API，直接使用 X11 原生 API。
+ */
+QPixmap ScreenGrabber::grabWithXGetImage(bool &ok, const QRect &rect)
+{
+    qCDebug(dsrApp) << "[XGetImage] Starting X11 screenshot for rect:" << rect;
+
+    Display *dpy = XOpenDisplay(nullptr);
+    if (!dpy) {
+        qCWarning(dsrApp) << "[XGetImage] Failed to open X11 Display";
+        ok = false;
+        return QPixmap();
+    }
+
+    Window root = DefaultRootWindow(dpy);
+
+    // 获取根窗口尺寸
+    XWindowAttributes rootAttr;
+    XGetWindowAttributes(dpy, root, &rootAttr);
+    qCDebug(dsrApp) << "[XGetImage] X11 root window size:" << rootAttr.width << "x" << rootAttr.height;
+
+    // 抓取整个根窗口
+    XImage *ximg = XGetImage(dpy, root, 0, 0, rootAttr.width, rootAttr.height, AllPlanes, ZPixmap);
+    if (!ximg) {
+        qCWarning(dsrApp) << "[XGetImage] XGetImage returned NULL";
+        XCloseDisplay(dpy);
+        ok = false;
+        return QPixmap();
+    }
+
+    qCDebug(dsrApp) << "[XGetImage] XImage captured, size:" << ximg->width << "x" << ximg->height
+                    << "depth:" << ximg->depth << "bits_per_pixel:" << ximg->bits_per_pixel;
+
+    // 将 XImage 转换为 QImage
+    QImage qimg(ximg->width, ximg->height, QImage::Format_RGB32);
+    for (int row = 0; row < ximg->height; ++row) {
+        for (int col = 0; col < ximg->width; ++col) {
+            unsigned long pixel = XGetPixel(ximg, col, row);
+            int r = (pixel >> 16) & 0xFF;
+            int g = (pixel >> 8) & 0xFF;
+            int b = pixel & 0xFF;
+            qimg.setPixel(col, row, qRgb(r, g, b));
+        }
+    }
+
+    XDestroyImage(ximg);
+    XCloseDisplay(dpy);
+
+    // 转换为 QPixmap
+    QPixmap fullPixmap = QPixmap::fromImage(qimg);
+    qCDebug(dsrApp) << "[XGetImage] Full pixmap size:" << fullPixmap.size();
+
+    // 如果请求的是整个桌面，直接返回
+    if (rect.isNull() || rect == QRect(0, 0, rootAttr.width, rootAttr.height)) {
+        qCDebug(dsrApp) << "[XGetImage] Returning full desktop screenshot";
+        ok = true;
+        return fullPixmap;
+    }
+
+    // 裁剪请求的区域
+    QRect cropRect = rect.intersected(QRect(0, 0, rootAttr.width, rootAttr.height));
+    if (cropRect.isEmpty()) {
+        qCWarning(dsrApp) << "[XGetImage] Crop rect is empty or outside root window";
+        ok = false;
+        return QPixmap();
+    }
+
+    QPixmap result = fullPixmap.copy(cropRect);
+    qCDebug(dsrApp) << "[XGetImage] Cropped result size:" << result.size();
+
+    ok = !result.isNull();
+    return result;
+}
+#endif

src/utils/screengrabber.h

@@ -10,7 +10,9 @@
 #include <QPixmap>
 #include <QRect>
 #include <QList>
-
+#if (QT_VERSION >= QT_VERSION_CHECK(6,0,0)) &&  defined(QT_QPA_PLATFORM_XCB)
+#define USE_X11_GETIMAGE 1
+#endif
 class QScreen;
 
 class ScreenGrabber : public QObject
@@ -28,6 +30,11 @@ class ScreenGrabber : public QObject
     QPixmap grabSingleScreen(bool &ok, const QRect &rect, QScreen *screen, const qreal devicePixelRatio);
     QPixmap grabMultipleScreens(bool &ok, const QRect &rect, const QList<QScreen*> &screens, const qreal devicePixelRatio);
     QPixmap grabScreenFragment(QScreen *screen, const QRect &intersection, const qreal devicePixelRatio);
+
+#ifdef USE_X11_GETIMAGE
+    // Qt6 X11 workaround: 使用 XGetImage 绕过 grabWindow 的 bug
+    QPixmap grabWithXGetImage(bool &ok, const QRect &rect);
+#endif
 };
 
 #endif // SCREENGRABBER_H