implement TransparentWindowBackground option

Signed-off-by: Yuhang Zhao <2546789017@qq.com>

include/FramelessHelper/Core/framelesshelpercore_global.h

@@ -192,7 +192,7 @@ enum class Option : int
     ForceShowWindowFrameBorder            = 0x00000002, // Windows only, force show the window frame border even on Windows 7 (~ 8.1).
     DontDrawTopWindowFrameBorder          = 0x00000004, // Windows only, don't draw the top window frame border even if the window frame border is visible.
     EnableRoundedWindowCorners            = 0x00000008, // Not implemented yet.
-    TransparentWindowBackground           = 0x00000010, // Not implemented yet.
+    TransparentWindowBackground           = 0x00000010, // Make the window's background become transparent.
     MaximizeButtonDocking                 = 0x00000020, // Not implemented yet.
     CreateStandardWindowLayout            = 0x00000040, // Using this option will cause FramelessHelper create a homemade titlebar and a window layout to contain it. If your window has a layout already, the newly created layout will mess up your own layout.
     BeCompatibleWithQtFramelessWindowHint = 0x00000080, // Windows only, make the code compatible with Qt::FramelessWindowHint. Don't use this option unless you really need that flag.

src/quick/framelessquickwindow.cpp

@@ -406,6 +406,12 @@ void FramelessQuickWindowPrivate::initialize()
     m_params.isInsideSystemButtons = [this](const QPoint &pos, SystemButtonType *button) -> bool { return isInSystemButtons(pos, button); };
     m_params.isInsideTitleBarDraggableArea = [this](const QPoint &pos) -> bool { return isInTitleBarDraggableArea(pos); };
     m_params.getWindowDevicePixelRatio = [q]() -> qreal { return q->effectiveDevicePixelRatio(); };
+    if (m_settings.options & Option::DisableResizing) {
+        setFixedSize(true, true);
+    }
+    if (m_settings.options & Option::TransparentWindowBackground) {
+        q->setColor(kDefaultTransparentColor);
+    }
     FramelessWindowsManager * const manager = FramelessWindowsManager::instance();
     manager->addWindow(m_settings, m_params);
     q->installEventFilter(this);
@@ -445,9 +451,6 @@ void FramelessQuickWindowPrivate::initialize()
     m_topBorderAnchors->setTop(rootItemPrivate->top());
     m_topBorderAnchors->setLeft(rootItemPrivate->left());
     m_topBorderAnchors->setRight(rootItemPrivate->right());
-    if (m_settings.options & Option::DisableResizing) {
-        setFixedSize(true, true);
-    }
 }
 
 QRect FramelessQuickWindowPrivate::mapItemGeometryToScene(const QQuickItem * const item) const

src/widgets/framelesswidgetshelper.cpp

@@ -393,6 +393,9 @@ void FramelessWidgetsHelper::initialize()
                           " Enabling this option will mess up with your main window's layout.";
         }
     }
+    if (m_settings.options & Option::TransparentWindowBackground) {
+        m_settings.options |= Option::BeCompatibleWithQtFramelessWindowHint;
+    }
     if (m_settings.options & Option::DisableResizing) {
         setFixedSize(true, true);
     }
@@ -400,6 +403,11 @@ void FramelessWidgetsHelper::initialize()
         Utils::tryToBeCompatibleWithQtFramelessWindowHint(windowId, m_params.getWindowFlags,
                                                           m_params.setWindowFlags, true);
     }
+    if (m_settings.options & Option::TransparentWindowBackground) {
+        q->setWindowFlags(q->windowFlags() | Qt::FramelessWindowHint);
+        q->setAttribute(Qt::WA_NoSystemBackground);
+        q->setAttribute(Qt::WA_TranslucentBackground);
+    }
     FramelessWindowsManager * const manager = FramelessWindowsManager::instance();
     manager->addWindow(m_settings, m_params);
     q->installEventFilter(this);