PixelShaderGen: only use dual-source if bpmem requires dual-src blending

[ligfx]

This fixes Issue 9373: Depth issues on Mario Kart Double Dash.

There seems to be some interaction between having ocol1 in the fragment shader and calling glBindFragDataLocationIndexed: removing either one fixes the issue. Adding stronger dual source requirements to the fragment shader seemed like the cleaner option.

Before:

After:

[iwubcode]

Seems fine to me but @stenzek or @degasus should give it a second look.

[CrossVR]

This seems redundant, why not just add MacOS to the BUG_BROKEN_DUAL_SOURCE_BLENDING in the driver details and update the description to make it more general?

[CrossVR]

To summarize what was discussed on IRC. I'd rather not add new UID fields. Another solution is to get rid of the glBindFragDataLocationIndexed calls by specifying the locations in the shader.

This requires OpenGL 3.3 however, so either we need to check if the relevant extension is supported or decide that OpenGL 3.3 is the minimum to run Dolphin. Also we need to check whether this is supported on OpenGL (ES) on Android.

[degasus]

always doing dual source blend was on purpose, as we want to use the color as blend factors with 24 bit accuracy and write the color with rgb565 accuracy.

[kemenaran]

Just tested this PR on macOS 10.12: I can confirm this fixes issue Issue 9373 (Depth issues on Mario Kart Double Dash), and similar depth issues on Mario Kart Wii.

@ligfx thank you so much for your work on this!

[ghost]

This can help my issue (dark blue filter overlay)?

Android 11
Vulkan
Mali-G52

[JosJuice]

@Gamemulatorer No.

[dreamsyntax]

@JMC47 please close this per https://bugs.dolphin-emu.org/issues/9373#note-20

[JosJuice]

Was this ever actually fixed in macOS OpenGL though?

[dreamsyntax]

Was this ever actually fixed in macOS OpenGL though?

I own this game and a mac, ill test and report back.

[dreamsyntax]

Works on an M1 Mac running Sequoia (15.2). Probably unrelated, I get a warning about performance so noting that here.
Stock Dolphin settings on 2412-183.

OpenGL

Metal

Oddly enough I get the same warning if I pick Metal, even though it says OpenGL in the warning.

[dreamsyntax]

Since the original image shows an Intel GPU, my above test may not be sufficient to confirm if it is resolved. Someone with an older mac with an Intel GPU would need to check.