创建具有帧缓冲区的xlib窗口，我可以直接绘制并使用XPutImage

Question

我正在尝试创建一个xlib窗口，创建一个深度为32的帧缓冲区，并将该缓冲区绘制到窗口中。一切正常，直到调用XPutImage，窗口从不显示，控制台输出：

Process returned -1 (0xFFFFFFFF) execution time : ?.??? s
Press ENTER to continue;

如果我注释掉Expose事件中的XPutImage行，那么我会得到一个具有透明客户端区域的窗口。所以我正在寻找如何解决这个问题的答案。

注意，我是Linux编程的新手，但已经做了很长时间的windows编程。所以我还不熟悉Linux的功能和协议；(

我在Fedora 32(64位(上使用Code:：Blocks 20.03。

代码：

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
int main(int argc, char **argv)
{
Display *dpy;
XVisualInfo vinfo;
int depth;
XVisualInfo *visual_list;
XVisualInfo visual_template;
int nxvisuals;
int i;
XSetWindowAttributes attrs;
Window parent;
Visual *visual;
int width, height;
Window win;
int *framebuf;
XImage *ximage;
XEvent event;
dpy = XOpenDisplay(NULL);
nxvisuals = 0;
visual_template.screen = DefaultScreen(dpy);
visual_list = XGetVisualInfo (dpy, VisualScreenMask, &visual_template, &nxvisuals);
for (i = 0; i < nxvisuals; ++i)
{
printf("  %3d: visual 0x%lx class %d (%s) depth %dn",
i,
visual_list[i].visualid,
visual_list[i].class,
visual_list[i].class == TrueColor ? "TrueColor" : "unknown",
visual_list[i].depth);
}
if (!XMatchVisualInfo(dpy, XDefaultScreen(dpy), 32, TrueColor, &vinfo))
{
fprintf(stderr, "no such visualn");
return 1;
}
printf("Matched visual 0x%lx class %d (%s) depth %dn",
vinfo.visualid,
vinfo.class,
vinfo.class == TrueColor ? "TrueColor" : "unknown",
vinfo.depth);
parent = XDefaultRootWindow(dpy);
XSync(dpy, True);
printf("creating RGBA childn");
visual = vinfo.visual;
depth = vinfo.depth;
attrs.colormap = XCreateColormap(dpy, XDefaultRootWindow(dpy), visual, AllocNone);
attrs.background_pixel = 0;
attrs.border_pixel = 0;
width = 1000;
height = 700;
framebuf = malloc((width*height)*4);
for (i = 0; i < (width*height); i++)
{
framebuf[i] = 0xFFFFFFFF;
}
win = XCreateWindow(dpy, parent, 100, 100, width, height, 0, depth, InputOutput,
visual, CWBackPixel | CWColormap | CWBorderPixel, &attrs);
ximage = XCreateImage(dpy, vinfo.visual, 32, XYPixmap, 0, (char *)framebuf, width, height, 8, width*4);
if (ximage == 0)
{
printf("ximage is null!n");
}
XSync(dpy, True);
XSelectInput(dpy, win, ExposureMask | KeyPressMask);
XGCValues gcv;
unsigned long gcm;
GC NormalGC;
//gcm = GCForeground | GCBackground | GCGraphicsExposures;
//gcv.foreground = BlackPixel(dpy, parent);
//gcv.background = WhitePixel(dpy, parent);
gcm = GCGraphicsExposures;
gcv.graphics_exposures = 0;
NormalGC = XCreateGC(dpy, parent, gcm, &gcv);
XMapWindow(dpy, win);
while(!XNextEvent(dpy, &event))
{
switch(event.type)
{
case Expose:
printf("I have been exposed!n");
XPutImage(dpy, win, NormalGC, ximage, 0, 0, 0, 0, width, height);
break;
}
}
printf("No errorn");
return 0;
}

Answer 1

为了让它工作起来，我不得不更改代码中的两行。你可能不会高兴，因为为了让它发挥作用，我不得不把它从RGBA改成BGRX。每当我使用xlib时，我总是必须使用24位深度，即使数据存储在32位中。它也存储BGRX而不是RGBX。。。

这是更改后的代码。

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
int main(int argc, char **argv)
{
Display *dpy;
XVisualInfo vinfo;
int depth;
XVisualInfo *visual_list;
XVisualInfo visual_template;
int nxvisuals;
int i;
XSetWindowAttributes attrs;
Window parent;
Visual *visual;
int width, height;
Window win;
int *framebuf;
XImage *ximage;
XEvent event;
dpy = XOpenDisplay(NULL);
nxvisuals = 0;
visual_template.screen = DefaultScreen(dpy);
visual_list = XGetVisualInfo (dpy, VisualScreenMask, &visual_template, &nxvisuals);
//Change to this line
//if (!XMatchVisualInfo(dpy, XDefaultScreen(dpy), 32, TrueColor, &vinfo))
if (!XMatchVisualInfo(dpy, XDefaultScreen(dpy), 24, TrueColor, &vinfo))
{
fprintf(stderr, "no such visualn");
return 1;
}
parent = XDefaultRootWindow(dpy);
XSync(dpy, True);
printf("creating RGBA childn");
visual = vinfo.visual;
depth = vinfo.depth;
attrs.colormap = XCreateColormap(dpy, XDefaultRootWindow(dpy), visual, AllocNone);
attrs.background_pixel = 0;
attrs.border_pixel = 0;
width = 1000;
height = 700;
framebuf = (int *) malloc((width*height)*4);
for (i = 0; i < (width*height); i++)
{
framebuf[i] = 0xFF00FFFF;
}
win = XCreateWindow(dpy, parent, 100, 100, width, height, 0, depth, InputOutput,
visual, CWBackPixel | CWColormap | CWBorderPixel, &attrs);
//Change to this line
//ximage = XCreateImage(dpy, vinfo.visual, 32, XYPixmap, 0, (char *)framebuf, width, height, 8, width*4);
ximage = XCreateImage(dpy, vinfo.visual, depth, ZPixmap, 0, (char *)framebuf, width, height, 8, width*4);
if (ximage == 0)
{
printf("ximage is null!n");
}
XSync(dpy, True);
XSelectInput(dpy, win, ExposureMask | KeyPressMask);
XGCValues gcv;
unsigned long gcm;
GC NormalGC;
//gcm = GCForeground | GCBackground | GCGraphicsExposures;
//gcv.foreground = BlackPixel(dpy, parent);
//gcv.background = WhitePixel(dpy, parent);
gcm = GCGraphicsExposures;
gcv.graphics_exposures = 0;
NormalGC = XCreateGC(dpy, parent, gcm, &gcv);
XMapWindow(dpy, win);
while(!XNextEvent(dpy, &event))
{
switch(event.type)
{
case Expose:
printf("I have been exposed!n");
XPutImage(dpy, win, NormalGC, ximage, 0, 0, 0, 0, width, height);
break;
}
}
printf("No errorn");
return 0;
}

Answer 2

您在XCreateGC(dpy, parent, gcm, &gcv);中使用的是父级的Drawable，而不是窗口自己的Drawable。

要使用32位颜色，请将其更改为XCreateGC(dpy, win, gcm, &gcv);