From 6f6f96909e7ded6ae3a4e59d9d4b62fa593abb23 Mon Sep 17 00:00:00 2001
From: Sine Striker <trueful@163.com>
Date: 周日, 25 2月 2024 02:33:03 +0800
Subject: [PATCH] Fix quick initialization failure

---
 src/widgets/widgetwindowagent_win.cpp |  142 +++++++++++++++++++++++++++++++----------------
 1 files changed, 93 insertions(+), 49 deletions(-)

diff --git a/src/widgets/widgetwindowagent_win.cpp b/src/widgets/widgetwindowagent_win.cpp
index 2733f94..791ed40 100644
--- a/src/widgets/widgetwindowagent_win.cpp
+++ b/src/widgets/widgetwindowagent_win.cpp
@@ -1,3 +1,7 @@
+// 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>
@@ -5,10 +9,33 @@
 #include <QtGui/QPainter>
 
 #include <QWKCore/qwindowkit_windows.h>
+#include <QWKCore/private/qwkglobal_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.
+
+    // 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.
+
+    // 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 NativeEventFilter, public SharedEventFilter {
     public:
@@ -21,6 +48,8 @@
             // Must extend top frame to client area
             static QVariant defaultMargins = QVariant::fromValue(QMargins(0, 1, 0, 0));
             ctx->setWindowAttribute(QStringLiteral("extra-margins"), defaultMargins);
+
+            // Enable dark mode by default, otherwise the system borders are white
             ctx->setWindowAttribute(QStringLiteral("dark-mode"), true);
 
             ctx->installNativeEventFilter(this);
@@ -43,33 +72,57 @@
             }
         }
 
+        inline void resumeWidgetEventAndDraw(QWidget *w, QEvent *event) {
+            // Let the widget paint first
+            static_cast<QObject *>(w)->event(event);
+
+            // 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.
+            ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
+        }
+
+        inline void resumeWindowEventAndDraw(QWindow *window, QEvent *event) {
+            // Let Qt paint first
+            static_cast<QObject *>(window)->event(event);
+
+            // 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.
+            ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
+        }
+
+        inline void updateExtraMargins(bool windowActive) {
+            if (windowActive) {
+                // Restore margins when the window is active
+                static QVariant defaultMargins = QVariant::fromValue(QMargins(0, 1, 0, 0));
+                ctx->setWindowAttribute(QStringLiteral("extra-margins"), defaultMargins);
+                return;
+            }
+
+            // https://github.com/microsoft/terminal/blob/71a6f26e6ece656084e87de1a528c4a8072eeabd/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp#L904
+            // When the window is inactive, there is a transparency bug in the top
+            // border, and we need to extend the non-client area to the whole title
+            // bar.
+            QRect frame = ctx->windowAttribute(QStringLiteral("window-rect")).toRect();
+            QMargins margins{0, -frame.top(), 0, 0};
+            ctx->setWindowAttribute(QStringLiteral("extra-margins"), QVariant::fromValue(margins));
+        }
+
     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();
+                    updateExtraMargins(widget->isActiveWindow());
                     break;
                 }
 
                 case WM_ACTIVATE: {
-                    if (LOWORD(msg->wParam) == WA_INACTIVE) {
-                        // https://github.com/microsoft/terminal/blob/71a6f26e6ece656084e87de1a528c4a8072eeabd/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp#L904
-                        // When the window is inactive, there is a transparency bug in the top
-                        // border, and we need to extend the non-client area to the whole title
-                        // bar.
-                        QRect frame =
-                            ctx->windowAttribute(QStringLiteral("title-bar-rect")).toRect();
-                        QMargins margins{0, -frame.top(), 0, 0};
-                        ctx->setWindowAttribute(QStringLiteral("extra-margins"),
-                                                QVariant::fromValue(margins));
-                    } else {
-                        // Restore margins when the window is active
-                        static QVariant defaultMargins = QVariant::fromValue(QMargins(0, 1, 0, 0));
-                        ctx->setWindowAttribute(QStringLiteral("extra-margins"), defaultMargins);
-                    }
+                    updateExtraMargins(LOWORD(msg->wParam) != WA_INACTIVE);
                     break;
                 }
 
@@ -83,51 +136,42 @@
             Q_UNUSED(obj)
 
             auto window = widget->windowHandle();
-            if (event->type() == QEvent::Expose) {
-                // Qt will absolutely send a QExposeEvent 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.
-                auto ee = static_cast<QExposeEvent *>(event);
-                if (isNormalWindow() && window->isExposed() && !ee->region().isNull()) {
-                    // Friend class helping to call `event`
-                    class HackedWindow : public QWindow {
-                    public:
-                        friend class QWK::WidgetBorderHandler;
-                    };
+            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.
 
-                    // Let Qt paint first
-                    static_cast<HackedWindow *>(window)->event(event);
-
-                    // Upon receiving the WM_PAINT message, Qt will redraw the entire view, and we
-                    // must wait for it to finish redrawing before drawing this top border area.
-                    ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
-                    return true;
+                    // Since a QExposeEvent will be sent immediately after the QResizeEvent, we can
+                    // simply ignore it.
+                    auto ee = static_cast<QExposeEvent *>(event);
+                    if (window->isExposed() && isNormalWindow() && !ee->region().isNull()) {
+                        resumeWindowEventAndDraw(window, event);
+                        return true;
+                    }
+                    break;
                 }
+                case QEvent::WinIdChange: {
+                    if (auto winId = ctx->windowId()) {
+                        updateGeometry();
+                    }
+                    break;
+                }
+                default:
+                    break;
             }
             return false;
         }
 
         bool eventFilter(QObject *obj, QEvent *event) override {
             Q_UNUSED(obj)
+
             switch (event->type()) {
                 case QEvent::UpdateRequest: {
                     if (!isNormalWindow())
                         break;
-
-                    // Friend class helping to call `event`
-                    class HackedWidget : public QWidget {
-                    public:
-                        friend class QWK::WidgetBorderHandler;
-                    };
-
-                    // Let the widget paint first
-                    static_cast<HackedWidget *>(widget)->event(event);
-
-                    // Due to the timer or user action, Qt will redraw some regions spontaneously,
-                    // even if there is no WM_PAINT message, we must wait for it to finish redrawing
-                    // and then update the top border area.
-                    ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
+                    resumeWidgetEventAndDraw(widget, event);
                     return true;
                 }
 

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