Route canvas mode and preview texture setup through helpers

docs/modernization/roadmap.md

@@ -3021,6 +3021,9 @@ Results:
   stroke composite shader setup helper, while render-task ordering, framebuffer
   copy bounds, sampler/texture binding, and draw execution remain in retained
   canvas-mode code.
+- `NodeStrokePreview::draw` now shares the retained draw-merge texture shader
+  setup helper for preview `Texture`, `Tex`, and `MVP` setup, while preview
+  texture binding, sampler binding, and draw execution remain in the node path.
 - `Canvas::import_layer` retained object drawing now shares the draw-merge
   texture shader setup helper for flat and spherical imports, while texture
   upload, sampler/texture binding, draw callbacks, and object geometry remain in
@@ -3048,6 +3051,10 @@ Results:
   share the retained draw-merge texture shader setup helper for `Texture`,
   `Tex`, and `MVP` setup. Texture/sampler binding, viewport/state setup, and
   draw execution remain in the node paths.
+- `CanvasModeTransform::on_Draw` and `CanvasModeFloodFill::on_Draw` now share
+  the retained draw-merge texture shader setup helper for `Texture`, `Tex`, and
+  `MVP` setup. Active texture selection, sampler/texture binding, and draw
+  execution remain in the canvas mode paths.
 - `Canvas::stroke_draw_mix` now shares the retained stroke composite shader
   helper for mixer-pass `CompDraw` setup, while preserving its caller-specific
   texture slot uniforms. Mixer framebuffer/scissor state, sampler and texture