PoC pixel-art mode

[skhoroshavin]

Proof of concept: when the Phaser game's pixelArt config flag is set, MSDF text switches to plain bitmap rendering - atlases upload with NEAREST filtering and the shader reads coverage straight from the texel alpha instead of the distance field. Everything in one draw call, as before.

What should work:

• Rich text end to end: per-run colors/alpha, per-run fonts (incl. merged atlases), fontScale, kerning, wrap
• Underline / strikethrough / highlight pills / dashed rules unchanged (they are shader-drawn rects, not texture data)
• Hard drop shadows (offset silhouette); glyph substitution, transforms, deform, all callbacks

What is disabled (one-time console warning if someone still tries to enable them):

• Weight, outline in all forms, soft/spread/rounded shadows, two-tone ramps - all distance-field based

What is left:

• Update to the actual demo
• Actual testing - there might still be edge cases, especially related to rounding or absence of it

[Antriel]

Talked with my robot about this a bit, I might end up trying something for pixelart when I will need it, meanwhile here are robot's notes:

Why not that PR

• NEAREST filtering is wrong for MSDF — linear interpolation of the field is the mechanism.
• texel.a is not a mask on any atlas msdf-atlas-gen emits: msdf → 255 everywhere, mtsdf → the true SDF, hardmask/softmask → greyscale PNG, so the mask is in RGB.
• Disables weight, outline, spread, rounded and two-tone — the features a pixel-art game most wants, and the ones BitmapText can't do.
• What remains is BitmapText: a baked mask, point-sampled, integer scales only. The MSDF does no work.
• Global game.config.pixelArt makes hasPixelArtChanged dead code — every binding gets the same value, the flush gate can never fire.
• Same flag forbids a pixel-art game from owning one smooth font.
• No demo, so it's unclear what atlas it was ever tested against.

Better direction

• Keep the field, harden the edge: one uSharpness uniform scaling the 1.0 AA floor in px, clamped to 4096 for mediump. That's the whole shader change.
• Per font, not per game or per object — rides the existing configureFont flush gate, and a smooth logo is just a different font.
• Declared at load (pixelGrid: 8 = design pixels per em), since no atlas JSON says "my outline is on an 8px grid".
• Weight, outline, spread, rounded, two-tone, hard shadow and animated scale all survive a threshold. Outline and animated scale are the two things BitmapText flatly cannot do.
• Exactness comes from three conditions: grid-aligned outline (pixel-font TTF), fontSize a multiple of the grid unit, integer pen. Meet them and edges land halfway between fragment centres — the most robust configuration, not a knife edge.
• The real work is layout, not shader: size quantization (incl. fitInside and fontScale), pen snapping in rebuildText only (after measurement, so the three-pass advance invariant holds), rounded alignment insets, snapped decoration rects.
• Generate atlases at or above the largest render size — minification is what produces the misplaced pixels you were worried about.
• PR PoC pixel-art mode #2's other feature — plain bitmap/hardmask atlas support — is worth having separately, and needs no shader branch at all: with zeroed params the existing lane already outputs a binary mask exactly.