X11-在叠加窗口上绘制 [英] X11 - Draw on Overlay Window

问题描述

我想在屏幕上的特定像素处绘制简单的图元(类似于此

I want to draw simple primitives at specific pixels on the screen (similar to this question). In order to do that I draw on top of all windows using the Overlay Window of the Window Manager. I can see the shape I am drawing and mouse events pass through but I don't see for example Window movements that are below the Overlay Window (unless I kill my application). I am new to Xlib programming, sry for asking a maybe simple question.

#include <assert.h>
#include <stdio.h>
#include <X11/Xlib.h>

#include <X11/extensions/Xcomposite.h>
#include <X11/extensions/Xfixes.h>
#include <X11/extensions/shape.h>

#include <cairo.h>
#include <cairo-xlib.h>

Display *d;
Window overlay;
Window root;
int width, height;

void
allow_input_passthrough (Window w)
{
    XserverRegion region = XFixesCreateRegion (d, NULL, 0);

    XFixesSetWindowShapeRegion (d, w, ShapeBounding, 0, 0, 0);
    XFixesSetWindowShapeRegion (d, w, ShapeInput, 0, 0, region);

    XFixesDestroyRegion (d, region);
}

void
prep_overlay (void)
{
    overlay = XCompositeGetOverlayWindow (d, root);
    allow_input_passthrough (overlay);
}

void draw(cairo_t *cr) {
    int quarter_w = width / 4;
    int quarter_h = height / 4;
    cairo_set_source_rgb(cr, 1.0, 0.0, 0.0);
    cairo_rectangle(cr, quarter_w, quarter_h, quarter_w * 2, quarter_h * 2);
    cairo_fill(cr);
}

int main() {
    d = XOpenDisplay(NULL);

    int s = DefaultScreen(d);
    root = RootWindow(d, s);

    XCompositeRedirectSubwindows (d, root, CompositeRedirectAutomatic);
    XSelectInput (d, root, SubstructureNotifyMask);

    width = DisplayWidth(d, s);
    height = DisplayHeight(d, s);

    prep_overlay();

    cairo_surface_t *surf = cairo_xlib_surface_create(d, overlay,
                                  DefaultVisual(d, s),
                                  width, height);
    cairo_t *cr = cairo_create(surf);

    XSelectInput(d, overlay, ExposureMask);

    draw(cr);

    XEvent ev;
    while (1) {
    XNextEvent(d, &ev);
        if (ev.type == Expose) {
            draw(cr);
        }
    }

    cairo_destroy(cr);
    cairo_surface_destroy(surf);
    XCloseDisplay(d);
    return 0;
}

如何在覆盖窗口上绘制像素并仍然看到下面的窗口?

How can I draw pixels on the Overlay Window and still see the windows below?

推荐答案

sleep(50)！太多了，只有50秒.我使用了5毫秒的延迟，效果很好.

sleep(50)! that's too much, it's 50 seconds. I used 5ms delay which works well.

您的问题似乎与运行时环境有关.您应该已经有一个复合显示管理器正在运行. (并非所有的展示广告管理器都能按预期工作，因此最好尝试其他展示广告管理器)

Your problem seems with the runtime environment. You should have a composite display manager running already. (Not all display managers work as expected, better to try on different ones)

我确认下面的屏幕已更新，没有任何问题，我可以与之互动.

I confirm that screen below updated without any problem and I could interact with it.

它运行于:

Ubuntu 15.10
Kernel 4.2.0-18-generic
X.Org X Server 1.17.2
Compiz 0.9.12.2

这里有完整的代码，只是进行了延迟修改:

Here the full code with just delay modification:

#include <assert.h>
#include <stdio.h>
#include <time.h>
#include <X11/Xlib.h>

#include <X11/extensions/Xcomposite.h>
#include <X11/extensions/Xfixes.h>
#include <X11/extensions/shape.h>

#include <cairo.h>
#include <cairo-xlib.h>

Display *d;
Window overlay;
Window root;
int width, height;

void
allow_input_passthrough (Window w)
{
    XserverRegion region = XFixesCreateRegion (d, NULL, 0);

    XFixesSetWindowShapeRegion (d, w, ShapeBounding, 0, 0, 0);
    XFixesSetWindowShapeRegion (d, w, ShapeInput, 0, 0, region);

    XFixesDestroyRegion (d, region);
}

void
prep_overlay (void)
{
    overlay = XCompositeGetOverlayWindow (d, root);
    allow_input_passthrough (overlay);
}

void draw(cairo_t *cr) {
    int quarter_w = width / 4;
    int quarter_h = height / 4;
    cairo_set_source_rgb(cr, 1.0, 0.0, 0.0);
    cairo_rectangle(cr, quarter_w, quarter_h, quarter_w * 2, quarter_h * 2);
    cairo_fill(cr);
}

int main() {
    struct timespec ts = {0, 5000000};

    d = XOpenDisplay(NULL);

    int s = DefaultScreen(d);
    root = RootWindow(d, s);

    XCompositeRedirectSubwindows (d, root, CompositeRedirectAutomatic);
    XSelectInput (d, root, SubstructureNotifyMask);

    width = DisplayWidth(d, s);
    height = DisplayHeight(d, s);

    prep_overlay();

    cairo_surface_t *surf = cairo_xlib_surface_create(d, overlay,
                                  DefaultVisual(d, s),
                                  width, height);
    cairo_t *cr = cairo_create(surf);

    XSelectInput(d, overlay, ExposureMask);

    draw(cr);

    XEvent ev;
    while(1) {
      overlay = XCompositeGetOverlayWindow (d, root);
      draw(cr);
      XCompositeReleaseOverlayWindow (d, root);
      nanosleep(&ts, NULL);
    }

    cairo_destroy(cr);
    cairo_surface_destroy(surf);
    XCloseDisplay(d);
    return 0;
}

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