fix: restore PDF plot scaling to fill available plot area (fixes #985) #987
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## Root Cause Analysis PDF scale regression introduced in commit 1c2fdea when aspect ratio preservation was added to coordinate transformation functions. This caused plots to appear smaller with centering instead of filling the plot area. **Before**: Coordinates used independent X/Y scales, filling plot area completely **After**: Used common scale (min of X/Y scales) for aspect ratio preservation ## Technical Fix Restored independent axis scaling in coordinate transformation: 1. **normalize_to_pdf_coords()**: Removed common_scale, centering offsets 2. **safe_coordinate_transform()**: Removed aspect ratio preservation logic 3. **Result**: PDF plots now fill available plot area like other backends ## Changes Made - Modified `src/backends/vector/fortplot_pdf_coordinate.f90`: - Removed aspect ratio preservation logic - Use independent x_scale and y_scale for each axis - Transform coordinates directly to fill plot area - Maintain epsilon protection for degenerate cases ## Validation - Created regression test demonstrating issue and fix - All tests pass with new coordinate transformation - PDF examples generate correctly scaled output - No impact on other backends (PNG/ASCII unaffected) ## Test Plan - [x] Run regression test to verify fix - [x] Run full test suite (all pass) - [x] Generate PDF examples to verify scaling - [x] Compare PDF output scale with PNG output (now consistent) 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>
This was referenced Aug 31, 2025
… PDF coordinate transform
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Summary
Fixes PDF scale regression where plots appeared smaller with centering instead of filling the available plot area. This regression was introduced ~2 weeks ago when aspect ratio preservation was added to PDF coordinate transformations.
Root Cause
The regression was introduced in commit 1c2fdea when aspect ratio preservation logic was added to
normalize_to_pdf_coords():common_scale = min(x_scale, y_scale)→ smaller plots with centeringTechnical Fix
Restored independent axis scaling in PDF coordinate transformations:
Modified Functions
normalize_to_pdf_coords(): Removed common scale, use separate x_scale/y_scalesafe_coordinate_transform(): Removed aspect ratio preservation logicKey Changes
Validation
test_pdf_scale_regression.f90demonstrating issue/fixFiles Changed
src/backends/vector/fortplot_pdf_coordinate.f90: Coordinate transformation fixexample/test_pdf_scale_regression.f90: Regression test for verificationTest Plan
🤖 Generated with Claude Code