fix: paper background no longer resizes when a viewport is added

White paper fill was calculated from entity bounding boxes (paper_entity_extents),
so adding a viewport caused the paper to visually shrink to the viewport's bounds.
Now paper_limits() (layout min/max limits) is used directly, and the unused
paper_entity_extents() function is removed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/properties.rs

@@ -312,7 +312,6 @@ impl H7CAD {
                 .add_entity_to_layout(entity, &layout)
             {
                 Ok(new_handle) => {
-                    // Auto-fit the new viewport to show model-space content.
                     self.tabs[i].scene.auto_fit_viewport(new_handle);
                 }
                 Err(e) => self

src/scene/mod.rs

@@ -2246,38 +2246,6 @@ impl Scene {
         self.wires_for_block(layout_block)
     }
 
-    /// Bounding box (min_x, min_y), (max_x, max_y) of all DXF entities in the
-    /// current paper layout, in paper-space coordinates.  Used by the 2-D canvas
-    /// to position the white paper fill so it aligns with the drawn entity borders.
-    /// Falls back to `paper_limits()` when the layout has no entities.
-    pub fn paper_entity_extents(&self) -> Option<((f32, f32), (f32, f32))> {
-        let layout_block = self.current_layout_block_handle();
-        let wires = self.wires_for_block(layout_block);
-
-        let mut min_x = f32::MAX;
-        let mut min_y = f32::MAX;
-        let mut max_x = f32::MIN;
-        let mut max_y = f32::MIN;
-
-        for wire in &wires {
-            for &[x, y, _] in &wire.points {
-                if x.is_finite() && y.is_finite() {
-                    min_x = min_x.min(x);
-                    min_y = min_y.min(y);
-                    max_x = max_x.max(x);
-                    max_y = max_y.max(y);
-                }
-            }
-        }
-
-        if min_x == f32::MAX {
-            // No entities — fall back to layout limits.
-            self.paper_limits()
-                .map(|((x0, y0), (x1, y1))| ((x0 as f32, y0 as f32), (x1 as f32, y1 as f32)))
-        } else {
-            Some(((min_x, min_y), (max_x, max_y)))
-        }
-    }
 
     /// Build a Camera oriented and scaled to match a paper-space Viewport entity.
     /// Used by `ViewportPane::Paper` to render model-space content through the

src/scene/paper_canvas.rs

@@ -68,9 +68,10 @@ impl<'a> canvas::Program<Message> for PaperCanvas<'a> {
         const DESK: Color = Color { r: 0.22, g: 0.24, b: 0.28, a: 1.0 };
         frame.fill_rectangle(Point::ORIGIN, bounds.size(), DESK);
 
-        // ── White paper area — use entity extents so the fill aligns with the
+        // ── White paper area — use layout paper limits (actual paper size).
-        //   drawn DXF entity borders (title block frame, viewport border, etc.).
+        if let Some(((px0, py0), (px1, py1))) = self.scene.paper_limits().map(
-        if let Some(((px0, py0), (px1, py1))) = self.scene.paper_entity_extents() {
+            |((x0, y0), (x1, y1))| ((x0 as f32, y0 as f32), (x1 as f32, y1 as f32)),
+        ) {
             let tl = to_px(px0, py1);
             let br = to_px(px1, py0);
             let pw = br.x - tl.x;