[FFmpeg-devel] [PATCH v4] gdigrab: Allow capturing a window by its handle

[Lena via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

Added more context in the error message and did a final test that it all works.

Thanks for the smooth patch submission process!


x11grab can capture windows by their ID, but gdigrab can only capture windows by their names, internally calling FindWindowW to lookup its handle.

This patch simply allows the user to specify a window handle directly.
Signed-off-by: Lena <lena@nihil.gay>
---
 doc/indevs.texi       |  8 ++++++--
 libavdevice/gdigrab.c | 15 ++++++++++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/doc/indevs.texi b/doc/indevs.texi
index 863536a34d..a0c684f545 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -722,7 +722,7 @@ Win32 GDI-based screen capture device.
 
 This device allows you to capture a region of the display on Windows.
 
-There are two options for the input filename:
+Amongst options for the imput filenames are such elements as:
 @example
 desktop
 @end example
@@ -730,9 +730,13 @@ or
 @example
 title=@var{window_title}
 @end example
+or
+@example
+hwnd=@var{window_hwnd}
+@end example
 
 The first option will capture the entire desktop, or a fixed region of the
-desktop. The second option will instead capture the contents of a single
+desktop. The second and third options will instead capture the contents of a single
 window, regardless of its position on the screen.
 
 For example, to grab the entire desktop using @command{ffmpeg}:
diff --git a/libavdevice/gdigrab.c b/libavdevice/gdigrab.c
index c069232472..aa909a9392 100644
--- a/libavdevice/gdigrab.c
+++ b/libavdevice/gdigrab.c
@@ -273,9 +273,22 @@ gdigrab_read_header(AVFormatContext *s1)
         }
     } else if (!strcmp(filename, "desktop")) {
         hwnd = NULL;
+    } else if (!strncmp(filename, "hwnd=", 5)) {
+        name = filename + 5;
+        char *p;
+
+        hwnd = strtol(name, &p, 0);
+
+        if (p == NULL || p == name || p[0] == '\0')
+        {
+            av_log(s1, AV_LOG_ERROR,
+                   "Invalid window handle '%s', must be an valid integer.\n", name);
+            ret = AVERROR(EINVAL);
+            goto error;
+        }
     } else {
         av_log(s1, AV_LOG_ERROR,
-               "Please use \"desktop\" or \"title=<windowname>\" to specify your target.\n");
+               "Please use \"desktop\", \"title=<windowname>\" or \"hwnd=<hwnd>\" to specify your target.\n");
         ret = AVERROR(EIO);
         goto error;
     }
-- 
2.43.0

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