From 953ebc40a8e26a388c454f7b05c598d5690840bc Mon Sep 17 00:00:00 2001
From: Sine Striker <trueful@163.com>
Date: 周二, 26 12月 2023 17:01:06 +0800
Subject: [PATCH] minor tweaks

---
 src/widgets/widgetwindowagent_win.cpp |  172 +++++++++++++++++++++++++++++++++++++++------------------
 1 files changed, 117 insertions(+), 55 deletions(-)

diff --git a/src/widgets/widgetwindowagent_win.cpp b/src/widgets/widgetwindowagent_win.cpp
index 173304f..52cc5ef 100644
--- a/src/widgets/widgetwindowagent_win.cpp
+++ b/src/widgets/widgetwindowagent_win.cpp
@@ -1,43 +1,101 @@
 #include "widgetwindowagent_p.h"
 
+#include <QtCore/QDebug>
+#include <QtCore/QDateTime>
 #include <QtGui/QPainter>
 
 #include <QWKCore/qwindowkit_windows.h>
-#include <QWKCore/qwkconfig.h>
-#include <QWKCore/private/nativeeventfilter_p.h>
 
 namespace QWK {
 
 #if QWINDOWKIT_CONFIG(ENABLE_WINDOWS_SYSTEM_BORDER)
+    // 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 redrawing.
+    //
+    // 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 redraw 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 NativeEventFilter, public SharedEventFilter {
     public:
-        explicit WidgetBorderHandler(QWidget *widget, AbstractWindowContext *ctx)
-            : QObject(ctx), widget(widget), ctx(ctx) {
+        explicit WidgetBorderHandler(QWidget *widget, AbstractWindowContext *ctx,
+                                     QObject *parent = nullptr)
+            : QObject(parent), widget(widget), ctx(ctx) {
             widget->installEventFilter(this);
 
+            // https://github.com/microsoft/terminal/blob/71a6f26e6ece656084e87de1a528c4a8072eeabd/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp#L940
+            // 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 frame borders are white
+            // ctx->setWindowAttribute(QStringLiteral("dark-mode"), true);
+
             ctx->installNativeEventFilter(this);
+            ctx->installSharedEventFilter(this);
+
             updateGeometry();
         }
 
         inline bool isNormalWindow() const {
-            return widget->windowState() &
-                   (Qt::WindowMinimized | Qt::WindowMaximized | Qt::WindowFullScreen);
+            return !(widget->windowState() &
+                     (Qt::WindowMinimized | Qt::WindowMaximized | Qt::WindowFullScreen));
         }
 
-        void updateGeometry() {
+        inline void updateGeometry() {
             if (isNormalWindow()) {
-                widget->setContentsMargins({
-                    0,
-                    ctx->property("borderThickness").toInt(),
-                    0,
-                    0,
-                });
+                widget->setContentsMargins(
+                    {0, ctx->windowAttribute(QStringLiteral("border-thickness")).toInt(), 0, 0});
             } else {
                 widget->setContentsMargins({});
             }
+        }
+
+        inline void resumeWidgetEvent(QWidget *w, QEvent *event) {
+            // Friend class helping to call `event`
+            class HackedWidget : public QWidget {
+            public:
+                friend class QWK::WidgetBorderHandler;
+            };
+
+            // Let the widget paint first
+            static_cast<HackedWidget *>(w)->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);
+        }
+
+        inline void resumeWindowEvent(QWindow *window, QEvent *event) {
+            // Friend class helping to call `event`
+            class HackedWindow : public QWindow {
+            public:
+                friend class QWK::WidgetBorderHandler;
+            };
+
+            // 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);
         }
 
     protected:
@@ -51,30 +109,23 @@
                     break;
                 }
 
-                case WM_THEMECHANGED:
-                case WM_SYSCOLORCHANGE:
-                case WM_DWMCOLORIZATIONCOLORCHANGED: {
-                    widget->update();
-                    break;
-                }
-
-                case WM_SETTINGCHANGE: {
-                    if (!msg->wParam && msg->lParam &&
-                        std::wcscmp(reinterpret_cast<LPCWSTR>(msg->lParam), L"ImmersiveColorSet") ==
-                            0) {
-                        widget->update();
+                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);
                     }
                     break;
-                }
-
-                case WM_PAINT: {
-                    // Let Qt paint first
-                    m_dispatcher->resume(eventType, message, result);
-
-                    // 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;
                 }
 
                 default:
@@ -83,23 +134,36 @@
             return false;
         }
 
+        bool sharedEventFilter(QObject *obj, QEvent *event) override {
+            Q_UNUSED(obj)
+
+            auto window = widget->windowHandle();
+
+            // 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.
+
+            // Since a QExposeEvent will be sent immediately after the QResizeEvent, we can simply
+            // ignore it.
+            if (event->type() == QEvent::Expose) {
+                auto ee = static_cast<QExposeEvent *>(event);
+                if (window->isExposed() && isNormalWindow() && !ee->region().isNull()) {
+                    resumeWindowEvent(window, event);
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
         bool eventFilter(QObject *obj, QEvent *event) override {
             Q_UNUSED(obj)
             switch (event->type()) {
                 case QEvent::UpdateRequest: {
-                    // 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);
-
-                    // 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 upper border area
-                    ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
+                    if (!isNormalWindow())
+                        break;
+                    resumeWidgetEvent(widget, event);
                     return true;
                 }
 
@@ -123,16 +187,14 @@
         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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