mirror of http://www.qtcentre.org/threads/55495-Non-client-area-painting-with-Qt

0-qt-render-non-client-windows.jpg

readme.md

This seems to be a rare example of painting to non-client area from a Qt application (on windows). I've mirrored it here because the original files were hidden behind an annoying sign-up process thing. I actually want to do this in PyQt - see also this SO question which is where I found the link to the qtforum posting.

Dear Qt Developers/Experts

My goal is to draw tabbar in titlebar (only in Windows) similar to firefox/chrome.
I am using some DWM apis to achieve that as mentioned in
http://msdn.microsoft.com/en-us/libr...=vs.85%29.aspx
Basically I make the entire area as nonclientarea and tabbar is drawn at the top automatically.

I know these DWM apis only work with Windows Aero enabled, and I am fine with tabbar
not shown in titlebar with DWM disabled.

I am facing two issues.
1. When the application is maximized, part of the left, top window portion 
gets clipped. See the attached image.
2. If I enable 'Auto hide taskbar' property in Windows, I would expect the
taskbar to popup when mouse is moved down near the taskbar with application 
maximized. That is not happening as well.

I have attached a sample project that creates the issue.
Can somebody help with this.
Any suggestions are welcome.

I can perfectly solve issue (1) with setContentsMargins() if I know the
exact amount of pixels that are being clipped.

Thanks
Rajendran

mainwindow.cpp

#include <QApplication>
#include <QTabWidget>
#include <QLineEdit>
#include <QDebug>
#include "mainwindow.h"
#include "Windows.h"
#include "WinUser.h"
#include "windowsx.h"
#include "dwmapi.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    setAttribute(Qt::WA_TranslucentBackground, true);

    QTabWidget *t = new QTabWidget(this);
    t->setTabsClosable(true);
    t->setMovable(true);
    t->setDocumentMode(true);
    t->addTab(new QLineEdit("1234"), "tab 1");
    t->addTab(new QLineEdit, "tab 2");
    t->addTab(new QLineEdit, "tab 3");
    t->addTab(new QLineEdit, "tab 4");

    this->setCentralWidget(t);
    resize(400,200);


    // Handle window creation.
    RECT rcClient;
    GetWindowRect(this->winId(), &rcClient);

    // Inform application of the frame change.
    SetWindowPos(this->winId(),
                 NULL,
                 rcClient.left, rcClient.top,
                 rcClient.right - rcClient.left,
                 rcClient.bottom - rcClient.top,
                 SWP_FRAMECHANGED);
}

bool MainWindow::winEvent(MSG *msg, long *result)
{
    bool fCallDWP = true;
    BOOL fDwmEnabled = FALSE;
    LRESULT lRet = 0;
    HRESULT hr = S_OK;
    HWND hWnd       = msg->hwnd;
    UINT message    = msg->message;
    WPARAM wParam   = msg->wParam;
    LPARAM lParam   = msg->lParam;

    // Winproc worker for custom frame issues.
    hr = DwmIsCompositionEnabled(&fDwmEnabled);
    if (!SUCCEEDED(hr) || !fDwmEnabled)
    {
        qDebug() << "DWM not enabled";
        return false;
    }

    fCallDWP = !DwmDefWindowProc(hWnd, message, wParam, lParam, &lRet);

    // Handle window activation.
    if (message == WM_ACTIVATE)
    {
        // Extend the frame into the client area.
        MARGINS margins;

        margins.cxLeftWidth = 8;      // 8
        margins.cxRightWidth = 8;    // 8
        margins.cyBottomHeight = 20; // 20
        margins.cyTopHeight = 27;       // 27

        hr = DwmExtendFrameIntoClientArea(hWnd, &margins);

        if (!SUCCEEDED(hr))
        {
            // Handle error.
        }

        fCallDWP = true;
        lRet = 0;
    }

    // Handle the non-client size message.
    if ((message == WM_NCCALCSIZE) && (wParam == TRUE))
    {
        qDebug() << "WM_NCCALCSIZE";
        // Calculate new NCCALCSIZE_PARAMS based on custom NCA inset.
        NCCALCSIZE_PARAMS *pncsp = reinterpret_cast<NCCALCSIZE_PARAMS*>(lParam);

        pncsp->rgrc[0].left   = pncsp->rgrc[0].left   + 0;
        pncsp->rgrc[0].top    = pncsp->rgrc[0].top    + 0;
        pncsp->rgrc[0].right  = pncsp->rgrc[0].right  - 0;
        pncsp->rgrc[0].bottom = pncsp->rgrc[0].bottom - 0;

        lRet = 0;

        // No need to pass the message on to the DefWindowProc.
        fCallDWP = false;
    }

    if (!fCallDWP)
        *result = lRet;

    return !fCallDWP;
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);

protected:
    bool winEvent(MSG *msg, long *result);
};

#endif // MAINWINDOW_H