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avdevice/xcbgrab: Add select_region option 

This patch adds a select_region option to the xcbgrab input device.
If set to 1, the user will be prompted to select the grabbing area
graphically by clicking and dragging. A rectangle will be drawn to
mark the grabbing area. A single click with no dragging will select
the whole screen. The option overwrites the video_size, grab_x, and
grab_y options if set by the user.

For testing, just set the select_region option as follows:

ffmpeg -f x11grab -select_region 1 -i :0.0 output.mp4

The drawing happens directly on the root window using standard rubber
banding techniques, so it is very efficient and doesn't depend on any
X extensions or compositors.

Reviewed-by: Andriy Gelman <andriy.gelman@gmail.com>
Signed-off-by: Omar Emara <mail@OmarEmara.dev>
This commit is contained in:
Omar Emara 2020-07-11 11:29:09 +02:00 committed by Andriy Gelman
parent c8101aabee
commit 04b37b5d7f
2 changed files with 130 additions and 0 deletions
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8
doc/indevs.texi
View File

@ -1503,6 +1503,14 @@ ffmpeg -f x11grab -framerate 25 -video_size cif -i :0.0+10,20 out.mpg
@subsection Options
@table @option
@item select_region
Specify whether to select the grabbing area graphically using the pointer.
A value of @code{1} prompts the user to select the grabbing area graphically
by clicking and dragging. A single click with no dragging will select the
whole screen. A region with zero width or height will also select the whole
screen. This option overwrites the @var{video_size}, @var{grab_x}, and
@var{grab_y} options. Default value is @code{0}.
@item draw_mouse
Specify whether to draw the mouse pointer. A value of @code{0} specifies
not to draw the pointer. Default value is @code{1}.

122
libavdevice/xcbgrab.c
View File

@ -22,6 +22,7 @@
#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <xcb/xcb.h>
#if CONFIG_LIBXCB_XFIXES
@ -69,6 +70,7 @@ typedef struct XCBGrabContext {
int show_region;
int region_border;
int centered;
int select_region;
const char *framerate;
@ -92,6 +94,7 @@ static const AVOption options[] = {
{ "centered", "Keep the mouse pointer at the center of grabbing region when following.", 0, AV_OPT_TYPE_CONST, { .i64 = -1 }, INT_MIN, INT_MAX, D, "follow_mouse" },
{ "show_region", "Show the grabbing region.", OFFSET(show_region), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, D },
{ "region_border", "Set the region border thickness.", OFFSET(region_border), AV_OPT_TYPE_INT, { .i64 = 3 }, 1, 128, D },
{ "select_region", "Select the grabbing region graphically using the pointer.", OFFSET(select_region), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, D },
{ NULL },
};
@ -677,6 +680,117 @@ static void setup_window(AVFormatContext *s)
draw_rectangle(s);
}
#define CROSSHAIR_CURSOR 34
static xcb_rectangle_t rectangle_from_corners(xcb_point_t *corner_a,
xcb_point_t *corner_b)
{
xcb_rectangle_t rectangle;
rectangle.x = FFMIN(corner_a->x, corner_b->x);
rectangle.y = FFMIN(corner_a->y, corner_b->y);
rectangle.width = FFABS(corner_a->x - corner_b->x);
rectangle.height = FFABS(corner_a->y - corner_b->y);
return rectangle;
}
static int select_region(AVFormatContext *s)
{
XCBGrabContext *c = s->priv_data;
xcb_connection_t *conn = c->conn;
xcb_screen_t *screen = c->screen;
int ret = 0, done = 0, was_pressed = 0;
xcb_cursor_t cursor;
xcb_font_t cursor_font;
xcb_point_t press_position;
xcb_generic_event_t *event;
xcb_rectangle_t rectangle = { 0 };
xcb_grab_pointer_reply_t *reply;
xcb_grab_pointer_cookie_t cookie;
xcb_window_t root_window = screen->root;
xcb_gcontext_t gc = xcb_generate_id(conn);
uint32_t mask = XCB_GC_FUNCTION | XCB_GC_SUBWINDOW_MODE;
uint32_t values[] = { XCB_GX_INVERT, XCB_SUBWINDOW_MODE_INCLUDE_INFERIORS };
xcb_create_gc(conn, gc, root_window, mask, values);
cursor_font = xcb_generate_id(conn);
xcb_open_font(conn, cursor_font, strlen("cursor"), "cursor");
cursor = xcb_generate_id(conn);
xcb_create_glyph_cursor(conn, cursor, cursor_font, cursor_font,
CROSSHAIR_CURSOR, CROSSHAIR_CURSOR + 1, 0, 0, 0,
0xFFFF, 0xFFFF, 0xFFFF);
cookie = xcb_grab_pointer(conn, 0, root_window,
XCB_EVENT_MASK_BUTTON_PRESS |
XCB_EVENT_MASK_BUTTON_RELEASE |
XCB_EVENT_MASK_BUTTON_MOTION,
XCB_GRAB_MODE_ASYNC, XCB_GRAB_MODE_ASYNC,
root_window, cursor, XCB_CURRENT_TIME);
reply = xcb_grab_pointer_reply(conn, cookie, NULL);
if (!reply || reply->status != XCB_GRAB_STATUS_SUCCESS) {
av_log(s, AV_LOG_ERROR,
"Failed to select region. Could not grab pointer.\n");
ret = AVERROR(EIO);
free(reply);
goto fail;
}
free(reply);
xcb_grab_server(conn);
while (!done && (event = xcb_wait_for_event(conn))) {
switch (event->response_type & ~0x80) {
case XCB_BUTTON_PRESS: {
xcb_button_press_event_t *press = (xcb_button_press_event_t *)event;
press_position = (xcb_point_t){ press->event_x, press->event_y };
rectangle.x = press_position.x;
rectangle.y = press_position.y;
xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
was_pressed = 1;
break;
}
case XCB_MOTION_NOTIFY: {
if (was_pressed) {
xcb_motion_notify_event_t *motion =
(xcb_motion_notify_event_t *)event;
xcb_point_t cursor_position = { motion->event_x, motion->event_y };
xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
rectangle = rectangle_from_corners(&press_position, &cursor_position);
xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
}
break;
}
case XCB_BUTTON_RELEASE: {
xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
done = 1;
break;
}
default:
break;
}
xcb_flush(conn);
free(event);
}
c->width = rectangle.width;
c->height = rectangle.height;
if (c->width && c->height) {
c->x = rectangle.x;
c->y = rectangle.y;
} else {
c->x = 0;
c->y = 0;
}
xcb_ungrab_server(conn);
xcb_ungrab_pointer(conn, XCB_CURRENT_TIME);
xcb_flush(conn);
fail:
xcb_free_cursor(conn, cursor);
xcb_close_font(conn, cursor_font);
xcb_free_gc(conn, gc);
return ret;
}
static av_cold int xcbgrab_read_header(AVFormatContext *s)
{
XCBGrabContext *c = s->priv_data;
@ -711,6 +825,14 @@ static av_cold int xcbgrab_read_header(AVFormatContext *s)
return AVERROR(EIO);
}
if (c->select_region) {
ret = select_region(s);
if (ret < 0) {
xcbgrab_read_close(s);
return ret;
}
}
ret = create_stream(s);
if (ret < 0) {