QT 一个桌面widget的实现方式

喜欢ヅ旅行 2022-09-13 15:25 135阅读 0赞

实现的效果类似桌面日历，当用户执行“显示桌面”时，这个widget仍然可以显示在桌面，而非最小化到任务栏。Windows系统，示例代码如下：

### desktopWidgetWin32.h ###

#pragma once
    #include <QWidget>
    #ifdef Q_OS_WIN
    #include "windows.h"
    
    bool enumUserWindowsCB(HWND hwnd, LPARAM lParam);
    
    void setParentDesktop(QWidget *pWidget);
    
    #endif //Q_OS_WIN

### desktopWidgetWin32.cpp ###

#include "desktopWidgetWin32.h"
    #ifdef Q_OS_WIN
    
    bool enumUserWindowsCB(HWND hwnd, LPARAM lParam)
    { 
    	long wflags = GetWindowLong(hwnd, GWL_STYLE);
    	if (!(wflags & WS_VISIBLE)) { 
    		return TRUE;
    	};
    
    	HWND sndWnd;
    	if (!(sndWnd = FindWindowEx(hwnd, NULL, L"SHELLDLL_DefView", NULL))) { 
    		return TRUE;
    	}
    	HWND targetWnd;
    	if (!(targetWnd = FindWindowEx(sndWnd, NULL, L"SysListView32", L"FolderView"))) { 
    		return TRUE;
    	}
    
    	HWND* resultHwnd = (HWND*)lParam;
    	*resultHwnd = targetWnd;
    	return FALSE;
    }
    
    void setParentDesktop(QWidget *pWidget)
    { 
    	HWND resultHwnd = NULL;
    	EnumWindows((WNDENUMPROC)enumUserWindowsCB, (LPARAM)&resultHwnd);
    
    	// 设置桌面为父窗口
    	if (resultHwnd) { 
    		SetParent((HWND)pWidget->winId(), resultHwnd);
    	}
    }
    #endif

### 如何使用？ ###

#include "QtDesktopWidgetDemo.h"
    #include "desktopWidgetWin32.h"
    #include <QVBoxLayout>
    #include <QPushButton>
    #include <QLabel>
    #include <QMouseEvent>
    #include <QGraphicsDropShadowEffect>
    
    QtDesktopWidgetDemo::QtDesktopWidgetDemo(QWidget *parent)
        : QWidget(parent)
    { 
    	setAttribute(Qt::WA_TranslucentBackground, true);
    	setWindowFlags(Qt::Window | Qt::FramelessWindowHint);	
    	setFixedSize(QSize(300, 200));
    
    	QWidget * centralWidget = new QWidget(this);
    	centralWidget->setStyleSheet("background: #eeeeee;");
    	QVBoxLayout * layoutInner = new QVBoxLayout();
    	layoutInner->addStretch(1);
    	
    	QLabel * label = new QLabel("Hello Kandy");
    	QFont font;
    	font.setPixelSize(16);
    	label->setFont(font);
    	layoutInner->addWidget(label);
    
    	QPushButton * button = new QPushButton("exit");
    	layoutInner->addWidget(button);
    	layoutInner->addStretch(1);
    	centralWidget->setLayout(layoutInner);
    
    	QGraphicsDropShadowEffect * shadow = new QGraphicsDropShadowEffect();
    	shadow->setColor(QColor(2, 122, 255, 255));//QColor("#444444")
    	shadow->setBlurRadius(20);
    	shadow->setOffset(0.0);
    	centralWidget->setGraphicsEffect(shadow);
    
    	QHBoxLayout * layoutMain = new QHBoxLayout();
    	layoutMain->setContentsMargins(0, 0, 0, 0);
    	layoutMain->addWidget(centralWidget);
    	this->setLayout(layoutMain);
    	this->setContentsMargins(25, 25, 25, 25);
    
    	connect(button, &QPushButton::clicked, []() { 
    		exit(0);
    	});
    
    	setParentDesktop(this);
    }
    
    void QtDesktopWidgetDemo::mousePressEvent(QMouseEvent *event)
    { 
    #ifdef Q_OS_WIN
    	if (ReleaseCapture())
    		SendMessage(HWND(winId()), WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
    	event->ignore();
    #endif
    }

### 最终效果 ###

当用户使用键盘按下“Win + D”时，其他程序全部隐藏，而此程序仍然可以显示在桌面上。  
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