When a paper-space viewport is activated (double-click / MSPACE command),
it is now rendered through its own dedicated PaperViewportPipeline rather
than the CPU-projection approach used for inactive viewports.
Architecture:
- PaperSheet widget (full-canvas): renders paper entities + CPU-projected
content of all viewports *except* the active one.
- PaperViewportPane widget (Fixed w×h, positioned at viewport screen rect):
renders the active viewport with a true 3D camera derived from the
viewport's view_direction/view_target/view_height.
PaperViewportPipeline is a newtype of Pipeline. Having a distinct type
gives it its own Iced storage entry (keyed by TypeId), preventing the
shared prepare() overwrite that broke the earlier per-viewport approach.
Changes:
- render.rs: PaperViewportPipeline, PaperViewportPrimitive newtypes;
build_active_viewport_primitive(); build_paper_sheet_primitive() now
excludes active_viewport from CPU projection.
- viewport_pane.rs: PaperViewportPane<'a> with shader::Program impl.
- mod.rs: viewport_content_wires() gains exclude_vp parameter;
viewport_screen_rect() is no longer dead code.
- view.rs: paper_canvas_view() overlays PaperViewportPane when MSPACE
is active.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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