+ ghosting from Gamate

[DnCraptor]

• bug-fix

[gemini-code-assist]

Summary of Changes

Hello @DnCraptor, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This PR refactors the ghosting implementation in the Gamate emulator, moving the logic into supervision_exec_ex for a more controlled and potentially improved visual effect. It updates the ghosting configuration, adjusts menu interaction for color editing, and modifies build settings.

Highlights

• Intent: This pull request aims to refactor and improve the ghosting effect implementation for Gamate emulation, addressing a potential bug and enhancing the visual quality of the ghosting. It also includes minor configuration and menu interaction improvements.
• Key Changes: The core ghosting logic has been completely rewritten and moved from gpu.c into supervision_exec_ex within watara.c. The new implementation utilizes intermediate expected_screen and rich_screen buffers to apply a more nuanced ghosting effect based on a ghosting parameter. The supervision_set_ghosting function and gpu_render_scanline have been removed, with the ghosting level now passed directly to supervision_exec_ex. Default ghosting settings have been adjusted (from 8 to 4), and the maximum configurable value in the menu is now 6, with a safeguard in load_config to cap older settings. Menu navigation has been refined, preventing movement while editing hex color values. Additionally, the CMakeLists.txt file was updated to set 'murmulator' as the default board and disable HDMI output.

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[gemini-code-assist]

Code Review

This pull request introduces a new ghosting effect and refactors how it's applied, which is a great improvement. However, I've found a few critical issues that will prevent the code from compiling or cause incorrect behavior at runtime. Please see my detailed comments below.

[gemini-code-assist]

The function signature for supervision_exec_ex has been updated to include a ghosting parameter, but not all call sites have been updated. The call within the #else block for non-VGA builds is still using the old signature, which will cause a compilation error.

// Around line 1253 in the new file
#else
    supervision_exec_ex((uint8_t *) SCREEN + 240 * 20 + 40, 240, 0);
#endif

Please update all calls to supervision_exec_ex to match the new four-argument signature.

[gemini-code-assist]

The loop for applying the ghosting effect has incorrect bounds. It iterates sizeof(rich_screen) times, which is a fixed 200 * 240 = 48000.

However, the actual rendered area is SV_H (160) lines high, and the memory layout of each line is determined by backbufferWidth. The preceding loop that populates expected_screen only processes this SV_H-line area.

This discrepancy will cause the loop to read from uninitialized parts of expected_screen and write beyond the intended area in backbuffer, leading to visual artifacts and undefined behavior.

The loop bounds should be based on the actual rendered area, which is SV_H * backbufferWidth.

        for (int i = 0; i < SV_H * backbufferWidth; ++i) {

[gemini-code-assist]

These changes to PICO_BOARD and the HDMI option (on line 51) appear to be local development configurations. They switch the default target board to murmulator and disable HDMI output.

Are these changes intended to be part of this pull request? If not, they should be reverted to avoid altering the default build configuration for other developers.