From 49b27d64a9778d53a3accd9bfbfbc3ee1a1a7178 Mon Sep 17 00:00:00 2001
From: Sine Striker <trueful@163.com>
Date: 周三, 08 5月 2024 20:44:05 +0800
Subject: [PATCH] minor tweaks

---
 src/widgets/widgetwindowagent_win.cpp |  171 +++++++++++++++++++++++++++++++++------------------------
 1 files changed, 99 insertions(+), 72 deletions(-)

diff --git a/src/widgets/widgetwindowagent_win.cpp b/src/widgets/widgetwindowagent_win.cpp
index 7901bac..7922cfe 100644
--- a/src/widgets/widgetwindowagent_win.cpp
+++ b/src/widgets/widgetwindowagent_win.cpp
@@ -1,102 +1,132 @@
+// Copyright (C) 2023-2024 Stdware Collections (https://www.github.com/stdware)
+// Copyright (C) 2021-2023 wangwenx190 (Yuhang Zhao)
+// SPDX-License-Identifier: Apache-2.0
+
 #include "widgetwindowagent_p.h"
 
+#include <QtCore/QDebug>
+#include <QtCore/QDateTime>
 #include <QtGui/QPainter>
 
+#include <QtCore/private/qcoreapplication_p.h>
+
 #include <QWKCore/qwindowkit_windows.h>
-#include <QWKCore/qwkconfig.h>
-#include <QWKCore/private/nativeeventfilter_p.h>
+#include <QWKCore/private/qwkglobal_p.h>
+#include <QWKCore/private/windows10borderhandler_p.h>
 
 namespace QWK {
 
-#if QWINDOWKIT_CONFIG(ENABLE_WINDOWS_SYSTEM_BORDER)
+#if QWINDOWKIT_CONFIG(ENABLE_WINDOWS_SYSTEM_BORDERS)
+    // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowsbackingstore.cpp#L42
+    // In QtWidgets applications, when repainting happens, QPA at the last calls
+    // QWindowsBackingStore::flush() to draw the contents of the buffer to the screen, we need to
+    // call GDI drawing the top border after that.
 
-    class WidgetBorderHandler;
+    // After debugging, we know that there are two situations that will lead to repaint.
+    //
+    // 1. Windows sends a WM_PAINT message, after which Qt immediately generates a QExposeEvent or
+    // QResizeEvent and send it to the corresponding QWidgetWindow instance, calling "flush" at the
+    // end of its handler.
+    //
+    // 2. When a timer or user input triggers Qt to repaint spontaneously, the corresponding
+    // QWidget receives a QEvent::UpdateRequest event and also calls "flush" at the end of its
+    // handler.
+    //
+    // The above two cases are mutually exclusive, so we just need to intercept the two events
+    // separately and draw the border area after the "flush" is called.
 
-    class WidgetBorderHandler : public QObject, public NativeEventFilter {
+    // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowswindow.cpp#L2440
+    // Note that we can not draw the border right after WM_PAINT comes or right before the WndProc
+    // returns, because Qt calls BeginPaint() and EndPaint() itself. We should make sure that we
+    // draw the top border between these two calls, otherwise some display exceptions may arise.
+
+    class WidgetBorderHandler : public QObject, public Windows10BorderHandler {
     public:
-        explicit WidgetBorderHandler(QWidget *widget, AbstractWindowContext *ctx)
-            : QObject(ctx), widget(widget), ctx(ctx) {
+        explicit WidgetBorderHandler(QWidget *widget, AbstractWindowContext *ctx,
+                                     QObject *parent = nullptr)
+            : QObject(parent), Windows10BorderHandler(ctx), widget(widget) {
             widget->installEventFilter(this);
 
-            ctx->installNativeEventFilter(this);
-            updateGeometry();
+            // First update
+            if (ctx->windowId()) {
+                setupNecessaryAttributes();
+            }
+            WidgetBorderHandler::updateGeometry();
         }
 
-        void updateGeometry() {
-            if (widget->windowState() & (Qt::WindowMaximized | Qt::WindowFullScreen)) {
-                widget->setContentsMargins({});
-            } else {
-                widget->setContentsMargins({
-                    0,
-                    ctx->property("borderThickness").toInt(),
-                    0,
-                    0,
-                });
+        void updateGeometry() override {
+            widget->setContentsMargins(isNormalWindow() ? QMargins(0, borderThickness(), 0, 0)
+                                                        : QMargins());
+        }
+
+        bool isWindowActive() const override {
+            return widget->isActiveWindow();
+        }
+
+        inline void forwardEventToWidgetAndDraw(QWidget *w, QEvent *event) {
+            // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/widgets/kernel/qapplication.cpp#L3286
+            // Deliver the event
+            if (!forwardObjectEventFilters(this, w, event)) {
+                // Let the widget paint first
+                std::ignore = static_cast<QObject *>(w)->event(event);
+                QCoreApplicationPrivate::setEventSpontaneous(event, false);
             }
+
+            // Due to the timer or user action, Qt will repaint some regions spontaneously,
+            // even if there is no WM_PAINT message, we must wait for it to finish painting
+            // and then update the top border area.
+            drawBorder();
+        }
+
+        inline void forwardEventToWindowAndDraw(QWindow *window, QEvent *event) {
+            // https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/widgets/kernel/qapplication.cpp#L3286
+            // Deliver the event
+            if (!forwardObjectEventFilters(ctx, window, event)) {
+                // Let Qt paint first
+                std::ignore = static_cast<QObject *>(window)->event(event);
+                QCoreApplicationPrivate::setEventSpontaneous(event, false);
+            }
+
+            // Upon receiving the WM_PAINT message, Qt will repaint the entire view, and we
+            // must wait for it to finish painting before drawing this top border area.
+            drawBorder();
         }
 
     protected:
-        bool nativeEventFilter(const QByteArray &eventType, void *message,
-                               QT_NATIVE_EVENT_RESULT_TYPE *result) override {
-            Q_UNUSED(eventType)
-            const auto msg = static_cast<const MSG *>(message);
-            switch (msg->message) {
-                case WM_DPICHANGED: {
-                    updateGeometry();
-                    break;
-                }
+        bool sharedEventFilter(QObject *obj, QEvent *event) override {
+            Q_UNUSED(obj)
 
-                case WM_THEMECHANGED:
-                case WM_SYSCOLORCHANGE:
-                case WM_DWMCOLORIZATIONCOLORCHANGED: {
-                    widget->update();
-                    break;
-                }
+            switch (event->type()) {
+                case QEvent::Expose: {
+                    // Qt will absolutely send a QExposeEvent or QResizeEvent to the QWindow when it
+                    // receives a WM_PAINT message. When the control flow enters the expose handler,
+                    // Qt must have already called BeginPaint() and it's the best time for us to
+                    // draw the top border.
 
-                case WM_SETTINGCHANGE: {
-                    if (!msg->wParam && msg->lParam &&
-                        std::wcscmp(reinterpret_cast<LPCWSTR>(msg->lParam), L"ImmersiveColorSet") ==
-                            0) {
-                        widget->update();
+                    // Since a QExposeEvent will be sent immediately after the QResizeEvent, we can
+                    // simply ignore it.
+                    auto ee = static_cast<QExposeEvent *>(event);
+                    auto window = widget->windowHandle();
+                    if (window->isExposed() && isNormalWindow() && !ee->region().isNull()) {
+                        forwardEventToWindowAndDraw(window, event);
+                        return true;
                     }
                     break;
                 }
-
                 default:
                     break;
             }
-            return false;
+            return Windows10BorderHandler::sharedEventFilter(obj, event);
         }
 
         bool eventFilter(QObject *obj, QEvent *event) override {
             Q_UNUSED(obj)
+
             switch (event->type()) {
-                case QEvent::Paint: {
-                    if (widget->windowState() &
-                        (Qt::WindowMinimized | Qt::WindowMaximized | Qt::WindowFullScreen))
+                case QEvent::UpdateRequest: {
+                    if (!isNormalWindow())
                         break;
-
-                    // Friend class helping to call `event`
-                    class HackedWidget : public QWidget {
-                    public:
-                        friend class WidgetBorderHandler;
-                    };
-
-                    // Let the widget paint first
-                    static_cast<HackedWidget *>(widget)->event(event);
-
-                    // Draw border
-                    auto paintEvent = static_cast<QPaintEvent *>(event);
-                    auto rect = paintEvent->rect();
-                    auto region = paintEvent->region();
-
-                    QPainter painter(widget);
-                    void *args[] = {
-                        &painter,
-                        &rect,
-                        &region,
-                    };
-                    ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook, args);
+                    forwardEventToWidgetAndDraw(widget, event);
                     return true;
                 }
 
@@ -118,18 +148,15 @@
         }
 
         QWidget *widget;
-        AbstractWindowContext *ctx;
     };
-#endif
 
     void WidgetWindowAgentPrivate::setupWindows10BorderWorkaround() {
-#if QWINDOWKIT_CONFIG(ENABLE_WINDOWS_SYSTEM_BORDER)
         // Install painting hook
         auto ctx = context.get();
-        if (ctx->property("needBorderPainter").toBool()) {
-            std::ignore = new WidgetBorderHandler(hostWidget, ctx);
+        if (ctx->windowAttribute(QStringLiteral("win10-border-needed")).toBool()) {
+            borderHandler = std::make_unique<WidgetBorderHandler>(hostWidget, ctx);
         }
-#endif
     }
+#endif
 
 }

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