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decorator: double-buffered output

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This patch ensures that the displayed pixel buffer is always consistent
by applying intermediate drawing steps on an invisible back buffer,
which is blitted to the front buffer by the GUI server.

Note that the addition of the back buffer increases the decorator's RAM
demand by 4*w*h (4 bytes per pixel) whereas w and h are the screen size.

Issue #5350
This commit is contained in:
Norman Feske 2024-09-23 17:43:22 +02:00 committed by Christian Helmuth
parent 8082aa980e
commit db2f1e542c
1 changed files with 39 additions and 9 deletions
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48
repos/gems/src/app/decorator/main.cc
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@ -60,29 +60,62 @@ struct Decorator::Main : Window_factory_base
Attached_dataspace fb_ds;
Decorator::Canvas<Pixel_rgb888> canvas;
/*
* The GUI connection's buffer is split into two parts. The upper
* part contains the front buffer displayed by the GUI server
* whereas the lower part contains the back buffer targeted by
* the Decorator::Canvas.
*/
Framebuffer::Mode _mode_doubled() const
{
return { { .w = mode.area.w, .h = mode.area.h*2 } };
}
Pixel_rgb888 *_canvas_pixels_ptr()
{
return fb_ds.local_addr<Pixel_rgb888>() + mode.area.count();
}
Canvas(Env &env, Gui::Connection &gui)
:
mode(gui.mode()),
fb_ds(env.rm(),
(gui.buffer(mode, false), gui.framebuffer.dataspace())),
canvas(fb_ds.local_addr<Pixel_rgb888>(), mode.area, env.ram(), env.rm())
(gui.buffer(_mode_doubled(), false), gui.framebuffer.dataspace())),
canvas(_canvas_pixels_ptr(), mode.area, env.ram(), env.rm())
{ }
};
Reconstructible<Canvas> _canvas { _env, _gui };
void _back_to_front(Dirty_rect dirty)
{
if (!_canvas.constructed())
return;
Rect const canvas_rect { { }, _canvas->mode.area };
dirty.flush([&] (Rect const &r) {
Rect const clipped = Rect::intersect(r, canvas_rect);
Point const from_p1 = clipped.p1() + Point { 0, int(canvas_rect.h()) };
Point const to_p1 = clipped.p1();
_gui.framebuffer.blit({ from_p1, clipped.area }, to_p1); });
}
Signal_handler<Main> _mode_handler { _env.ep(), *this, &Main::_handle_mode };
void _handle_mode()
{
_canvas.construct(_env, _gui);
_window_stack.mark_as_dirty(Rect(Point(0, 0), _canvas->mode.area));
Area const canvas_area = _canvas->mode.area;
_window_stack.mark_as_dirty(Rect(Point(0, 0), canvas_area));
Dirty_rect dirty = _window_stack.draw(_canvas->canvas);
dirty.flush([&] (Rect const &r) {
_gui.framebuffer.refresh(r); });
_back_to_front(dirty);
}
Window_stack _window_stack = { *this };
@ -316,13 +349,10 @@ void Decorator::Main::_handle_gui_sync()
if (model_updated || windows_animated) {
Dirty_rect dirty = _window_stack.draw(_canvas->canvas);
_back_to_front(dirty);
_window_stack.update_gui_views();
_gui.execute();
dirty.flush([&] (Rect const &r) {
_gui.framebuffer.refresh(r); });
}
/*