feat: Add subplot support with grid layouts (#62)

* feat: Add subplot support with grid layouts and independent axes

- Implement subplot_t type to manage individual subplot properties
- Add subplots() method to create grid layouts (rows x cols)
- Add subplot_plot() to add plots to specific subplots
- Add subplot_set_title/xlabel/ylabel for subplot labeling
- Add subplot rendering with independent coordinate systems
- Create comprehensive test suite covering all subplot features
- Add demo showing 2x2 and 1x3 subplot layouts

Each subplot maintains its own:
- Data ranges and axis limits
- Title and axis labels
- Plot collection
- Pixel boundaries for rendering

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Address critical subplot rendering issues

- Fix critical bug: Check allocation before linestyle comparison to prevent crashes
- Implement proper coordinate transformation for subplot rendering
- Fix empty subplot handling with default ranges
- Add transform_subplot_coordinates function for proper data-to-screen mapping
- Ensure all subplots render with axes even when empty

This addresses the critical allocation bug flagged in PR review.

* fix: Implement proper subplot coordinate transformation

- Set backend coordinate system for each subplot
- Use proper apply_scale_transform for subplot rendering
- Remove unused transform_subplot_coordinates function
- Fix coordinate mapping to work with existing backend system

This addresses the rendering shortcut that caused blank subplot images.

* Rebrand from fortplotlib to fortplot

- Renamed all occurrences of 'fortplotlib' to 'fortplot' throughout codebase
- Updated package name in fpm.toml, pyproject.toml, and CMakeLists.txt
- Renamed Python package directory from python/fortplotlib to python/fortplot
- Updated all documentation, README files, and examples
- Updated GitHub repository URLs in documentation
- Maintained consistency with existing module name 'fortplot'

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Update subplot demo output paths for FORD documentation compatibility

- Change output paths from plots/ to build/example/subplot_demo/
- Add subplot_demo directory to Makefile build targets
- Ensure FORD can discover subplot demo plots in expected location

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Update fpm example dependency to use local path

- Change dependency from git URL to local path reference
- Fixes test_system_fpm_example failure
- All tests now pass

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Fix subplot rendering to properly isolate plot regions

- Update backend plot_area for each subplot to constrain drawing
- Save and restore plot_area when switching between subplots
- Add proper subplot coordinate system setup for PNG and PDF backends
- Fix subplot rendering so plots appear in correct regions
- Add debug_subplot app for testing subplot functionality

Previously all subplot plots were rendered in the same space. Now each
subplot is properly isolated to its designated region.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Complete subplot rendering with proper axes and titles

- Fixed subplot isolation by updating backend plot_area for each subplot
- Replaced simple rectangle drawing with proper axes functions (draw_axes_and_labels)
- Implemented separate subplot title rendering positioned above each subplot
- Increased vertical gap between subplots from 0.05 to 0.08 for better title spacing
- Titles now properly positioned: first row at y=25px (like main title), other rows centered in gap
- All subplots now render with independent axes, tick marks, labels, and titles

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Improve subplot title positioning with proper margins

- Simplified title positioning to use consistent 20px padding above subplot top
- Increased top margin from 5% to 10% when using subplots to accommodate titles
- Removed complex conditional positioning logic
- Ensures titles stay within image bounds (minimum y=15px)
- Follows matplotlib's approach of consistent padding above axes

This fixes the issue where subplot titles were not visible or were being clipped
due to insufficient top margin space.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Render subplot titles directly to image buffer for PNG backend

- Fixed subplot title rendering by using render_text_to_image directly
- Bypassed coordinate transformation that was causing incorrect positioning
- Titles now render properly in screen coordinates above each subplot
- Simplified implementation by removing unused LaTeX processing for now

The issue was that the text() method applies data-to-screen transformation,
but subplot titles need to be positioned in screen coordinates directly.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Clean up subplot title rendering implementation

- Removed debug print statements and boxes
- Simplified implementation for production use
- Subplot titles now render correctly above each subplot
- Using render_text_to_image directly for PNG backend

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix: Use old library name in CMake example until rename is merged

The main branch still uses 'fortplotlib' as the library name, so the CMake
example needs to use that name when fetching from main. This will be updated
back to 'fortplot' once the rename is merged to main.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* chore: Clean up debug print statements and TODOs

- Removed debug print statements from debug_subplot.f90
- Removed unnecessary print statements from subplot_demo.f90
- Cleaned up TODO comment about LaTeX processing
- Kept error handling print statements (consistent with codebase pattern)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: krystophny

AGENTS.md

@@ -29,7 +29,7 @@ These are not suggestions - they are strict requirements that MUST be followed i
 
 ## Project Overview
 
-**fortplotlib** is a modern Fortran plotting library providing scientific visualization with PNG, PDF, and ASCII backends.
+**fortplot** is a modern Fortran plotting library providing scientific visualization with PNG, PDF, and ASCII backends.
 
 ## API Usage
 

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.20)
-project(fortplotlib VERSION 2025.06.25 LANGUAGES Fortran C)
+project(fortplot VERSION 2025.06.25 LANGUAGES Fortran C)
 
 # Set default build type
 if(NOT CMAKE_BUILD_TYPE)
@@ -12,39 +12,39 @@ set(CMAKE_Fortran_FLAGS_DEBUG "-g -O0 -fcheck=all")
 set(CMAKE_Fortran_FLAGS_RELEASE "-O3")
 
 # Automatically collect all source files from src directory
-file(GLOB_RECURSE FORTPLOTLIB_SOURCES "src/*.f90" "src/*.c")
+file(GLOB_RECURSE FORTPLOT_SOURCES "src/*.f90" "src/*.c")
 
 # Create static library
-add_library(fortplotlib STATIC ${FORTPLOTLIB_SOURCES})
+add_library(fortplot STATIC ${FORTPLOT_SOURCES})
 
 # Set module directory and enable position-independent code for shared library usage
-set_target_properties(fortplotlib PROPERTIES
+set_target_properties(fortplot PROPERTIES
     Fortran_MODULE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/include
     POSITION_INDEPENDENT_CODE ON
 )
 
 # Make modules available to consumers
-target_include_directories(fortplotlib
+target_include_directories(fortplot
     PUBLIC 
         $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>
         $<INSTALL_INTERFACE:include>
 )
 
 # Create alias for FetchContent compatibility
-add_library(fortplotlib::fortplotlib ALIAS fortplotlib)
+add_library(fortplot::fortplot ALIAS fortplot)
 
 # Export targets for FetchContent
-export(TARGETS fortplotlib
-    NAMESPACE fortplotlib::
-    FILE ${CMAKE_CURRENT_BINARY_DIR}/fortplotlibTargets.cmake
+export(TARGETS fortplot
+    NAMESPACE fortplot::
+    FILE ${CMAKE_CURRENT_BINARY_DIR}/fortplotTargets.cmake
 )
 
 # Check if Python interface should be built
 if (ENABLE_PYTHON)
     include(cmake/PythonHelpers.cmake)
     add_f90wrap_wrapper(
         fortplot_wrapper
-        fortplotlib
+        fortplot
         src/fortplot.f90
     )
     # After f90wrap generates files, fix the imports

Makefile

@@ -25,9 +25,9 @@ debug:
 test:
 	fpm test $(FPM_FLAGS) $(ARGS)
 
-# Run Python examples with fortplotlib (default mode)
+# Run Python examples with fortplot (default mode)
 example_python:
-	@echo "Running Python examples with fortplotlib..."
+	@echo "Running Python examples with fortplot..."
 	@for dir in example/python/*/; do \
 		if [ -f "$$dir"*.py ]; then \
 			echo "Running $$dir"; \
@@ -104,13 +104,14 @@ create_build_dirs:
 	@mkdir -p build/example/smart_show_demo
 	@mkdir -p build/example/animation
 	@mkdir -p build/example/stateful_streamplot
+	@mkdir -p build/example/subplot_demo
 
 # Help target
 help:
 	@echo "Available targets:"
 	@echo "  build            - Compile the project"
 	@echo "  example          - Build and run all Fortran examples"
-	@echo "  example_python   - Run Python examples with fortplotlib"
+	@echo "  example_python   - Run Python examples with fortplot"
 	@echo "  example_matplotlib - Run Python examples with matplotlib (comparison)"
 	@echo "  debug            - Build and run apps for debugging"
 	@echo "  test             - Run all tests"

README.md

@@ -1,9 +1,9 @@
-# ![fortplotlib logo](media/logo.jpg)
+# ![fortplot logo](media/logo.jpg)
 
-[![codecov](https://codecov.io/gh/krystophny/fortplotlib/branch/main/graph/badge.svg)](https://codecov.io/gh/krystophny/fortplotlib)
-[![Documentation](https://img.shields.io/badge/docs-FORD-blue.svg)](https://krystophny.github.io/fortplotlib/)
+[![codecov](https://codecov.io/gh/krystophny/fortplot/branch/main/graph/badge.svg)](https://codecov.io/gh/krystophny/fortplot)
+[![Documentation](https://img.shields.io/badge/docs-FORD-blue.svg)](https://krystophny.github.io/fortplot/)
 
-Fortran-native plotting inspired by Python's `matplotlib.pyplot` and https://github.com/jacobwilliams/pyplot-fortran . This library is under active development and API still subject to change. There are no external dependencies. Ironically, it has also Python interface installable via `pip` (see below) `fortplotlib.fortplot` that can be used as a drop-in replacement for `matplotlib.pyplot` for a limited set of features.
+Fortran-native plotting inspired by Python's `matplotlib.pyplot` and https://github.com/jacobwilliams/pyplot-fortran . This library is under active development and API still subject to change. There are no external dependencies. Ironically, it has also Python interface installable via `pip` (see below) `fortplot.fortplot` that can be used as a drop-in replacement for `matplotlib.pyplot` for a limited set of features.
 
 ## Usage
 
@@ -111,7 +111,7 @@ to build and run them.
 Add to your `fpm.toml`:
 ```toml
 [[dependencies]]
-fortplotlib = { git = "https://github.com/krystophny/fortplotlib" }
+fortplot = { git = "https://github.com/krystophny/fortplot" }
 ```
 
 ### For CMake projects
@@ -121,20 +121,20 @@ Add to your `CMakeLists.txt`:
 include(FetchContent)
 
 FetchContent_Declare(
-    fortplotlib
-    GIT_REPOSITORY https://github.com/krystophny/fortplotlib
+    fortplot
+    GIT_REPOSITORY https://github.com/krystophny/fortplot
     GIT_TAG        main
 )
-FetchContent_MakeAvailable(fortplotlib)
+FetchContent_MakeAvailable(fortplot)
 
-target_link_libraries(your_target fortplotlib::fortplotlib)
+target_link_libraries(your_target fortplot::fortplot)
 ```
 
 ### For Python projects
 Install the Python package with pip:
 
 ```bash
-pip install git+https://github.com/krystophny/fortplotlib.git
+pip install git+https://github.com/krystophny/fortplot.git
 ```
 
 ## Features

app/debug_subplot.f90

@@ -0,0 +1,44 @@
+program debug_subplot
+    use iso_fortran_env, only: real64, wp => real64
+    use fortplot, only: figure_t
+    implicit none
+    
+    type(figure_t) :: fig
+    real(wp) :: x(10), y(10)
+    integer :: i, j
+    
+    ! Simple test data
+    do i = 1, 10
+        x(i) = real(i, wp)
+        y(i) = real(i, wp)
+    end do
+    
+    ! Test 1: Simple 2x1 subplot
+    call fig%initialize(800, 400)
+    call fig%subplots(1, 2)
+    
+    ! Add plot to first subplot
+    call fig%subplot_plot(1, 1, x, y, label='Linear')
+    call fig%subplot_set_title(1, 1, 'First Plot')
+    
+    ! Add plot to second subplot  
+    call fig%subplot_plot(1, 2, x, y**2, label='Quadratic')
+    call fig%subplot_set_title(1, 2, 'Second Plot')
+    
+    ! Save the figure
+    call fig%savefig('debug_subplot_test.png')
+    
+    ! Test 2: 2x2 subplot
+    call fig%initialize(800, 800)
+    call fig%subplots(2, 2)
+    
+    do i = 1, 2
+        do j = 1, 2
+            call fig%subplot_plot(i, j, x, x**(real(i+j-1, wp)), label='Power')
+            call fig%subplot_set_title(i, j, 'Subplot ' // char(48+i) // ',' // char(48+j))
+        end do
+    end do
+    
+    call fig%savefig('debug_subplot_2x2.png')
+    
+end program debug_subplot

doc.md

@@ -1,4 +1,4 @@
-Welcome to the fortplotlib documentation. This library provides a modern, matplotlib-inspired plotting interface for Fortran with multiple backends including PNG, PDF, and ASCII.
+Welcome to the fortplot documentation. This library provides a modern, matplotlib-inspired plotting interface for Fortran with multiple backends including PNG, PDF, and ASCII.
 
 ## Features
 

doc/cmake_example/CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.20)
-project(fortplotlib_cmake_example Fortran)
+project(fortplot_cmake_example Fortran)
 
 # Enable Fortran
 enable_language(Fortran)
@@ -10,16 +10,16 @@ include(FetchContent)
 # Fetch and build fortplotlib using CMake
 FetchContent_Declare(
     fortplotlib
-    GIT_REPOSITORY https://github.com/krystophny/fortplotlib
+    GIT_REPOSITORY https://github.com/krystophny/fortplot
     GIT_TAG main
 )
 FetchContent_MakeAvailable(fortplotlib)
 
 # Create a simple test program
-add_executable(fortplotlib_test main.f90)
+add_executable(fortplot_test main.f90)
 
-# Link against fortplotlib
-target_link_libraries(fortplotlib_test fortplotlib::fortplotlib)
+# Link against fortplotlib (using old name until rename is merged to main)
+target_link_libraries(fortplot_test fortplotlib::fortplotlib)
 
 # Set Fortran compiler flags
 set(CMAKE_Fortran_FLAGS "-Wall -Wextra -fimplicit-none")

doc/design/axes_layout.md

@@ -2,7 +2,7 @@
 
 ## Overview
 
-This document describes the matplotlib-compatible axes and layout management system in fortplotlib, covering coordinate systems, axis scaling, tick generation, spine rendering, and layout optimization. The implementation follows matplotlib's Axes class architecture and transform system patterns while maintaining Fortran's performance characteristics.
+This document describes the matplotlib-compatible axes and layout management system in fortplot, covering coordinate systems, axis scaling, tick generation, spine rendering, and layout optimization. The implementation follows matplotlib's Axes class architecture and transform system patterns while maintaining Fortran's performance characteristics.
 
 ## Problem Statement
 
@@ -461,4 +461,4 @@ end subroutine
 - **`test/test_transforms.f90`** - Coordinate transformation verification
 - **`test/test_tight_layout.f90`** - Layout optimization algorithm tests
 
-This implementation ensures fortplotlib provides matplotlib-compatible axes and layout management with professional coordinate systems, flexible spine positioning, automatic layout optimization, and complete multi-axes support for complex scientific visualization workflows.
+This implementation ensures fortplot provides matplotlib-compatible axes and layout management with professional coordinate systems, flexible spine positioning, automatic layout optimization, and complete multi-axes support for complex scientific visualization workflows.

doc/design/backends.md

@@ -2,7 +2,7 @@
 
 ## Overview
 
-This document describes the matplotlib-compatible backend architecture in fortplotlib, covering rendering systems, output formats, and drawing primitives. The implementation follows matplotlib's three-layer backend architecture while leveraging Fortran's polymorphism and type safety for high-performance scientific visualization.
+This document describes the matplotlib-compatible backend architecture in fortplot, covering rendering systems, output formats, and drawing primitives. The implementation follows matplotlib's three-layer backend architecture while leveraging Fortran's polymorphism and type safety for high-performance scientific visualization.
 
 ## Problem Statement
 
@@ -490,4 +490,4 @@ end subroutine
 - **`test/test_drawing_primitives.f90`** - Drawing API compliance tests
 - **`test/test_performance_backends.f90`** - Backend performance benchmarks
 
-This implementation ensures fortplotlib provides matplotlib-compatible backend architecture with professional rendering capabilities, flexible output format support, sophisticated graphics state management, and high-performance optimization for scientific visualization workflows.
+This implementation ensures fortplot provides matplotlib-compatible backend architecture with professional rendering capabilities, flexible output format support, sophisticated graphics state management, and high-performance optimization for scientific visualization workflows.

doc/design/basic_plots.md

@@ -2,7 +2,7 @@
 
 ## Overview
 
-This document describes the matplotlib-compatible basic plotting implementation in fortplotlib, covering line plots, scatter plots, and bar charts. The implementation follows matplotlib's API and behavior exactly to ensure drop-in compatibility and familiar user experience.
+This document describes the matplotlib-compatible basic plotting implementation in fortplot, covering line plots, scatter plots, and bar charts. The implementation follows matplotlib's API and behavior exactly to ensure drop-in compatibility and familiar user experience.
 
 ## Problem Statement
 
@@ -294,8 +294,8 @@ end function
 - **`src/fortplot_markers.f90`** - Extended marker support and rendering
 - **`src/fortplot_linestyles.f90`** - Complete line style implementations
 - **`src/fortplot_colors.f90`** - Color cycle and named color support
-- **`python/fortplotlib/fortplot.py`** - Updated Python interface
+- **`python/fortplot/fortplot.py`** - Updated Python interface
 - **`test/test_basic_plots.f90`** - Comprehensive plotting tests
 - **`test/test_format_parser.f90`** - Format string parsing verification
 
-This implementation ensures fortplotlib provides matplotlib-compatible basic plotting functionality with professional rendering quality and complete API compatibility for seamless migration from matplotlib-based workflows.
+This implementation ensures fortplot provides matplotlib-compatible basic plotting functionality with professional rendering quality and complete API compatibility for seamless migration from matplotlib-based workflows.