Details
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Bug
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Resolution: Unresolved
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P2: Important
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None
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6.5.8
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Linux/Wayland,
Description
On some systems (custom yocto, Ubuntu 22.04 with nested Qt Wayland Compositor) an example like this stops for 100ms when opening a window in a Wayland Compositor:
import QtQuick import QtQuick.Controls Window { width: 800 height: 400 visible: true Window { id: other } Button { onClicked: { other.visible = true } } }
With WAYLAND_DEBUG and QSG_RENDER_TIMING enabled, it is visible like this:
qt.scenegraph.time.glyph: distancefield: 35 glyphs prepared in 4ms, rendering=2, upload=2 qt.scenegraph.time.renderer: time in renderer: total=1ms, preprocess=0, updates=0, rendering=1 qt.scenegraph.time.texture: atlastexture upload enqueued in: -9223363746551ms (32x18) qt.scenegraph.time.texture: atlastexture upload enqueued in: -9223363746551ms (32x18) qt.scenegraph.time.renderer: time in renderer: total=11ms, preprocess=1, updates=0, rendering=10 [1555328.539] -> wl_surface@31.frame(new id wl_callback@28) [1555328.618] -> zwp_linux_dmabuf_v1@5.create_params(new id zwp_linux_buffer_params_v1@38) [1555328.714] -> zwp_linux_buffer_params_v1@38.add(fd 58, 0, 0, 5120, 16777216, 4) [1555328.802] -> zwp_linux_buffer_params_v1@38.add(fd 60, 1, 3276800, 256, 16777216, 4) [1555328.867] -> zwp_linux_buffer_params_v1@38.create_immed(new id wl_buffer@39, 1280, 640, 875713089, 0) [1555328.928] -> zwp_linux_buffer_params_v1@38.destroy() [1555328.948] -> wl_surface@31.attach(wl_buffer@39, 0, 0) [1555328.990] -> wl_surface@31.damage(0, 0, 2147483647, 2147483647) [1555329.062] -> wl_surface@31.commit() [1555329.079] -> wl_display@1.sync(new id wl_callback@40) qt.scenegraph.time.renderloop: [window 0x55644251d4f0][gui thread] syncAndRender: frame rendered in 88ms, polish=9, sync=23, render=28, swap=27, perWindowFrameDelta=235 qt.scenegraph.time.renderer: time in renderer: total=0ms, preprocess=0, updates=0, rendering=0 [1555339.661] wl_display@1.delete_id(35) [1555339.725] wl_display@1.delete_id(36) [1555339.733] wl_display@1.delete_id(37) [1555339.739] wl_display@1.delete_id(38) [1555339.745] wl_display@1.delete_id(40) [1555432.204] wl_callback@40.done(245) [1555432.258] -> zwp_linux_dmabuf_v1@5.create_params(new id zwp_linux_buffer_params_v1@40) [1555432.314] -> zwp_linux_buffer_params_v1@40.add(fd 58, 0, 0, 5120, 16777216, 4) [1555432.360] -> zwp_linux_buffer_params_v1@40.add(fd 60, 1, 3276800, 256, 16777216, 4) [1555432.396] -> zwp_linux_buffer_params_v1@40.create_immed(new id wl_buffer@38, 1280, 640, 875713089, 0) [1555432.433] -> zwp_linux_buffer_params_v1@40.destroy() [1555432.442] -> wl_surface@31.attach(wl_buffer@38, 0, 0) [1555432.464] -> wl_surface@31.damage(0, 0, 2147483647, 2147483647) [1555432.515] -> wl_surface@31.commit() [1555432.524] -> wl_display@1.sync(new id wl_callback@37) qt.scenegraph.time.renderloop: [window 0x55644251d4f0][gui thread] syncAndRender: frame rendered in 103ms, polish=0, sync=0, render=0, swap=102, perWindowFrameDelta=103 qt.scenegraph.time.renderer: time in renderer: total=0ms, preprocess=0, updates=0, rendering=0 [1555439.121] wl_display@1.delete_id(40) [1555439.170] wl_display@1.delete_id(37) [1555535.497] wl_buffer@39.release() [1555535.535] wl_callback@37.done(245) [1555535.561] -> zwp_linux_dmabuf_v1@5.create_params(new id zwp_linux_buffer_params_v1@37) [1555535.622] -> zwp_linux_buffer_params_v1@37.add(fd 58, 0, 0, 5120, 16777216, 4) [1555535.663] -> zwp_linux_buffer_params_v1@37.add(fd 60, 1, 3276800, 256, 16777216, 4) [1555535.709] -> zwp_linux_buffer_params_v1@37.create_immed(new id wl_buffer@40, 1280, 640, 875713089, 0) [1555535.745] -> zwp_linux_buffer_params_v1@37.destroy() [1555535.753] -> wl_surface@31.attach(wl_buffer@40, 0, 0) [1555535.774] -> wl_surface@31.damage(0, 0, 2147483647, 2147483647) [1555535.824] -> wl_surface@31.commit() [1555535.834] -> wl_display@1.sync(new id wl_callback@36) qt.scenegraph.time.renderloop: [window 0x55644251d4f0][gui thread] syncAndRender: frame rendered in 103ms, polish=0, sync=0, render=0, swap=102, perWindowFrameDelta=103
With QT_LOGGING_RULES=qt.qpa.wayland.backingstore.debug=true set, the issue seems to point to waiting in QWaylandWindow::waitForFrameSync():
qt.qpa.wayland.backingstore: handleUpdate QSGRenderThread(0x61100198e200) qt.qpa.wayland.backingstore: requestUpdate qt.qpa.wayland.backingstore: Didn't receive frame callback in time, window should now be inexposed qt.qpa.wayland.backingstore: handleUpdate QSGRenderThread(0x61100198e200) qt.qpa.wayland.backingstore: Didn't receive frame callback in time, window should now be inexposed qt.qpa.wayland.backingstore: handleUpdate QSGRenderThread(0x61100198e200) qt.qpa.wayland.backingstore: deliverUpdateRequest
Looks like it does not have this issue when running with basic render loop.