Allegro backend has corrupt text in 1.92.0

[Espyo]

Version/Branch of Dear ImGui:

1.92.0

Back-ends:

imgui_impl_allegro5.cpp

Compiler, OS:

Ubuntu 22.04 + g++ 12.3

Full config/build information:

No response

Details:

My Issue/Question:

When compiling and running the Allegro 5 example in the repository, everything looks okay at first, but clicking on any of the tree nodes will cause all text to become corrupted.

More Info:

• Dear ImGui repository: commit 85b2fe8 (version 1.92.0 tag)
• Allegro version: 5.2.7
• Compiling and running under commit f5befd2 (version 1.91.9b tag) works as expected

Screenshots/Video:

Minimal, Complete and Verifiable Example code:

No response

[ocornut]

Hello,

Thanks for your report.
This is almost certainly caused by the code in ee8941e. However I cannot seem to reproduce the issue locally. (Using Allegro 5.2.10 as installed by vcpkg on Windows).

Based on https://www.allegro.cc/manual/5/al_lock_bitmap
I would imagine that we should use ALLEGRO_LOCK_READWRITE in the call to al_lock_bitmap_region() performed in the ImTextureStatus_WantUpdates block inside ImGui_ImplAllegro5_UpdateTexture() - instead of ALLEGRO_LOCK_WRITEONLY.
Could you confirm?

[ocornut]

I have 99% sure that using ALLEGRO_LOCK_READWRITE would have fixed it, but I am pushing an alternative fix which is updating the whole rectangle anyway: 57a93e1 and can keep using ALLEGRO_LOCK_WRITEONLY.
I am confident this would work but please confirm if it doesn't!