使用X11的Xcomposite扩展获取隐藏或不可见或最小化的窗口的屏幕截图 [英] Get a screenshot of a window that is cover or not visible or minimized with Xcomposite extension for X11
问题描述
我有以下起始代码来获取X窗口的屏幕截图(该窗口可以覆盖,不可见或最小化).
I have the follow starting code to get a screenshot of a X window (the window can be covered, not visibled, or minimized).
#include <stdlib.h>
#include <stdio.h>
#include <X11/Xlib.h>
#include <X11/X.h>
#include <X11/extensions/Xcomposite.h>
#include <X11/extensions/Xrender.h>
int
main ()
{
Display *display = XOpenDisplay (NULL);
XID xid = 90177543; // xdotool search --name "World of Warcraft" | head -1
// Check if Composite extension is enabled
int event_base_return;
int error_base_return;
if (XCompositeQueryExtension (display, &event_base_return, &error_base_return))
printf ("COMPOSITE IS ENABLED!\n");
// Requests the X server to direct the hierarchy starting at window to off-screen storage
XCompositeRedirectWindow (display, xid, CompositeRedirectAutomatic);
// Preventing the backing pixmap from being freed when the window is hidden/destroyed
// If you want the window contents to still be available after the window has been destroyed,
// or after the window has been resized (but not yet redrawn), you can increment the backing
// pixmaps ref count to prevent it from being deallocated.
Pixmap pixmap = XCompositeNameWindowPixmap (display, xid);
// Get window attributes
XWindowAttributes attr;
Status s = XGetWindowAttributes (display, xid, &attr);
if (s == 0)
printf ("Fail to get window attributes!\n");
// Extract the data
XRenderPictFormat *format = XRenderFindVisualFormat (display, attr.visual);
int width = attr.width;
int height = attr.height;
int depth = attr.depth;
// What we need to do now is to create an XRender Picture for the window,
// which we'll need to draw it with the Render extension.
// A picture is a basically a handle to a server side struct with some
// additional information about a drawable (in this case a window),
// such as its format, which clipping region should be used when
// drawing it (if any), whether it should be tiled etc.
XRenderPictureAttributes pa;
pa.subwindow_mode = IncludeInferiors;
Picture picture = XRenderCreatePicture (display, xid, format, CPSubwindowMode, &pa);
// We now have all the information we need in order to be able to draw the window
// using the Xrender extension, and we've created and prepared a source picture
// for the window for this purpose.
// The Xrender function we'll use to draw the window is XRenderComposite().
//XRenderComposite (display, PictOpSrc, picture, None, ???destination???, 0,0, 0,0, 0,0, width, height);
XFreePixmap (display, pixmap);
XCompositeUnredirectWindow (display, xid, CompositeRedirectAutomatic);
return 0;
}
[使用gcc file.c -lX11 -lXcomposite -lXrender
编译代码并使用./a.out
运行]
[Compile the code with gcc file.c -lX11 -lXcomposite -lXrender
and run with ./a.out
]
[您可以使用命令xdotool search --name "Title of a window" | head -1
获取桌面窗口的有效XID]
[You can get a valid XID of a window of your Desktop with the command xdotool search --name "Title of a window" | head -1
]
现在我有两个问题:
- 调用
XRenderFindVisualFormat
函数时出现BadMatch (invalid parameter attributes)
错误.我不知道为什么.存在XID 90177543的窗口. - 我不知道如何获取
Picture picture
的缓冲区以将其另存为PNG图像.我不想使用QT库来做到这一点.
- I get a
BadMatch (invalid parameter attributes)
error when I call theXRenderFindVisualFormat
function. I dont know why. The window with XID 90177543 exists. - I don't know how to get the buffer of the
Picture picture
to save it as a PNG image. I don't want use QT library to do this.
你能帮我吗?
推荐答案
我能够按照以下方式重现您的错误:
I am able to reproduce your error as follows:
$ ./xidtest
COMPOSITE IS ENABLED!
X Error of failed request: BadWindow (invalid Window parameter)
Major opcode of failed request: 142 (Composite)
Minor opcode of failed request: 1 ()
Resource id in failed request: 0x5600007
Serial number of failed request: 9
Current serial number in output stream: 12
使用我知道存在的窗口ID进行设置(使用xwininfo找到的0x440000B或71303179)时,我没有收到错误:
When set using a window id I knew to exist (0x440000B or 71303179, found using xwininfo), I received no error:
$ ./xidtest
COMPOSITE IS ENABLED!
我认为错误是您提供的窗口ID无效.
I conclude that the error is the window id you have provided is invalid.
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