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Fix Inaccurate Window Movement in Linux Framebuffer Backend #107

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Fix Inaccurate Window Movement in Linux Framebuffer Backend #107

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3 changes: 2 additions & 1 deletion backend/fbdev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -190,7 +190,8 @@ static bool twin_fbdev_update_damage(void *closure)
twin_fbdev_t *tx = PRIV(closure);
twin_screen_t *screen = SCREEN(closure);

if (!tx->vt_active && twin_screen_damaged(screen))
if (!tx->vt_active && (tx->fb_base == MAP_FAILED) &&
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@jserv jserv Jun 28, 2025 •
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Should the condition tx->fb_base == MAP_FAILED be considered as an early return?

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I experimented based on the following code and found that the issue still persists.

--- a/backend/fbdev.c
+++ b/backend/fbdev.c
@@ -190,6 +190,9 @@ static bool twin_fbdev_update_damage(void *closure)
     twin_fbdev_t *tx = PRIV(closure);
     twin_screen_t *screen = SCREEN(closure);
 
+    if (tx->fb_base == MAP_FAILED)
+       return;
+
     if (!tx->vt_active && twin_screen_damaged(screen))
         twin_screen_update(screen);

twin_screen_damaged(screen))
twin_screen_update(screen);

return true;
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