如何在多监视器系统上检测最大化事件

Question

在windows上，当系统有多个监视器时，C/C++如何检测WM_WINDOWPOSCHANGING消息上的"最大化事件"？也就是说，当窗口在任何显示器上最大化时？

（也欢迎其他操作系统的代码！）

Answer 1

首先需要使用EnumDisplayDevices和EnumDisplaySettingsEx检测所有显示器。

// C/C++ solution for enumerating display settings.
// Struct for display properties
struct DisplayProps
{
    int x, y;   // only display position is needed..
};
DISPLAY_DEVICE disp;
DISPLAY_DEVICE adapter;
DEVMODE mode;
DisplayProps the_displays[32];  // Array to store the results.
int i = 0, j = 0, display_count = 0;
// Initialize win32 structs.
memset(&disp, 0, sizeof(DISPLAY_DEVICE));
disp.cb = sizeof(DISPLAY_DEVICE);
memset(&args.adapter, 0, sizeof(DISPLAY_DEVICE));
adapter.cb = sizeof(DISPLAY_DEVICE);
memset(&mode, 0, sizeof(DEVMODE));
mode.dmSize = sizeof(DEVMODE);
memset(the_displays, 0, sizeof(the_displays));
// adapter loop:
while(EnumDisplayDevices(NULL, i, &adapter, 0))
{   // multiple displays on single adapter loop:
    j = 0;
    while(EnumDisplayDevices((TCHAR*)&adapter.DeviceName, j, &disp, 0))
    {   
        // The device must be active, attached to desktop and not a mirroring device.
        if((disp.StateFlags & DISPLAY_DEVICE_ACTIVE)
            && (disp.StateFlags & DISPLAY_DEVICE_ATTACHED_TO_DESKTOP)
            && !(disp.StateFlags & DISPLAY_DEVICE_MIRRORING_DRIVER))
        {
            // read display settings.
            if(EnumDisplaySettingsEx((TCHAR*)&adapter.DeviceName, ENUM_CURRENT_SETTINGS, &mode, 0))
            {
                the_displays[display_count].x = mode.dmPosition.x;
                the_displays[display_count].y = mode.dmPosition.y;
                ++display_count;
            }
        }
        // Reset
        memset(&args.disp, 0, sizeof(DISPLAY_DEVICE));
        disp.cb = sizeof(DISPLAY_DEVICE);
        ++j;
    }
    // Reset
    memset(&args.adapter, 0, sizeof(DISPLAY_DEVICE));
    adapter.cb = sizeof(DISPLAY_DEVICE);
    ++i;
}

然后，在窗口过程中的WM_WINDOWPOSCHANGING消息上，我们需要实际检测事件。这需要一个可能未记录的值SWP_STATECHANGED（0x8000）和使用AdjustWindowRectEx。

WINDOWPOS * wp = (WINDOWPOS*)lParam;
if( (wp->flags & (SWP_STATECHANGED | SWP_FRAMECHANGED)) != 0)
{
    // Figuring next part was a bit of luck involved: I noticed that AdjustWindowRectEx rect.left
    // matches window position (x and y) on default display when window is maximized
    RECT styleadj = {0, 0, 0, 0};
    // Can't cache/save this because user can change the theme.
    AdjustWindowRectEx(&styleadj,
    WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX, /* your window dwStyle */
    false, /* not using menu? */
    WS_EX_APPWINDOW | WS_EX_WINDOWEDGE); /* your window dwExStyle */ 
    for(int i = 0; i < the_display_count; ++i)
    {
        if((wp->x == the_displays[i].x + styleadj.left) && (wp->y == the_displays[i].y + styleadj.left))
        {
            // Event is detected, do what ever you want!
            MessageBox(NULL, "A Maximize event Detected.", "Event Detected!", MB_OK);
        }
    }
}

我已经确认此代码适用于多个显示器（我有两个），并且适用于Windows 7 Aero Glass主题、Aero Basic主题和旧的win 2000主题。WinXp和8未经测试。AdjustWindowRectEx确实在不同的主题上返回不同的值。

Answer 2

当窗口要最大化时，特别是由于交互式用户操作，它会收到WM_SYSCOMMAND SC_MAXIMIZE消息。

最大化过程通常涉及WM_GETMINMAXINFO消息，处理。。。

应用程序可以使用此消息覆盖窗口的默认最大大小和位置，或其默认的最小或最大跟踪大小。

检测当前监视器工作区域坐标可能最简单的是MonitorFromRect API:

HMONITOR hMonitor = MonitorFromRect(&rcCenter, MONITOR_DEFAULTTONEAREST);
if(hMonitor)
{
    MONITORINFO MonitorInfo = { sizeof MonitorInfo };
    GetMonitorInfo(hMonitor, &MonitorInfo);
    // NOTE: MonitorInfo.rcWork is what you look for