DrawTool

A feature-rich interactive drawing tool built with OpenGL and GLUT.

About

DrawTool is an OpenGL-based drawing application that lets you create, edit, and export shapes interactively. It features a persistent shape model with undo/redo, layer support, SVG and PNG export, keyboard shortcuts, and a HUD overlay.

Features

Drawing Tools

• Line -- click and drag
• Circle -- outline or filled, click and drag
• Rectangle -- outline or filled, click and drag
• Triangle -- outline or filled, 3-click vertex placement
• Freehand Pen -- continuous polyline from mouse motion
• Arrow -- line with arrowhead
• Bezier Curve -- 4-click control point placement
• Text -- click to place, type on keyboard, Enter to commit

Editing

• Selection tool -- click a shape to select it (highlighted in white dashes)
• Move -- drag a selected shape, or use arrow keys (5px steps)
• Delete -- press Delete/Backspace to remove the selected shape
• Undo / Redo -- unlimited history via Ctrl+Z / Ctrl+Y
• Clear All -- right-click menu or programmatic reset

Rendering

• Line styles -- solid, dashed, dotted stipple patterns
• Line width -- configurable 1-8 px from menu
• Polygon modes -- front/back face rendering as fill, line, or point
• Shading -- flat or smooth
• Colors -- seven preset colors via right-click menu
• Layers -- 4 layers (0-3); shapes render back-to-front by layer
• Double buffering -- flicker-free rendering

Export / Import

• Save PNG -- Ctrl+S exports a timestamped PNG screenshot
• Save SVG -- Ctrl+E exports drawing.svg with shape metadata
• Load SVG -- Ctrl+O reloads drawing.svg (round-trip preserving types and colors)

HUD

A translucent top bar shows the current tool, shape count, active layer, and a color swatch.

Scripted / Headless Mode

Run DrawTool without a GUI via --script:

./build/drawtool --script demos/sample.dtxt

Script DSL commands:

Command	Example
line	line 10 20 100 200
circle	circle 150 150 50 fill
rect	rect 200 200 300 300 fill
triangle	triangle 0 0 100 0 50 80
arrow	arrow 0 0 200 200
text	text 50 100 "Hello"
color	color 1.0 0.0 0.0
linewidth	linewidth 3
layer	layer 2
undo / redo	undo
clear	clear
save	save output.svg
width / height	width 1024
quit	quit

Lines starting with # are comments. See demos/ for examples.

Feature Tour

See docs/feature-tour.svg for a visual walkthrough of the application's UI, tools, and keyboard shortcuts.

Keyboard Shortcuts

Key	Action
1	Line tool
2	Circle outline
3	Circle fill
4	Rectangle outline
5	Rectangle fill
6	Triangle outline
7	Triangle fill
8	Freehand pen
9	Arrow
0	Select / Move tool
Ctrl+Z	Undo
Ctrl+Y	Redo
Ctrl+S	Save PNG
Ctrl+E	Save SVG
Ctrl+O	Load SVG
Delete / Backspace	Delete selected shape
Arrow keys	Move selected shape (5px)
Escape	Cancel text input
Enter	Commit text
Right-click	Context menu

File Layout

File	Purpose
CMakeLists.txt	Cross-platform build (macOS, Linux, Windows)
openGL5/main.cpp	Entry point, display, keyboard, menus
openGL5/app.h	DrawingApp singleton encapsulating all state
openGL5/shape.h	Shape struct, undo/redo stack
openGL5/mouse.h	Mouse button and motion callbacks
openGL5/process.h	Shape renderer (layer-sorted)
openGL5/selection.h	Menu callback handlers
openGL5/hittest.h	Geometry hit-testing (point-in-rect, point-on-line, etc.)
openGL5/save.h	SVG save and load
openGL5/png_export.h	PNG export via stb_image_write
openGL5/stb_image_write.h	Single-header PNG writer (vendored)
openGL5/script.h	Headless script interpreter (--script mode)
tests/geometry_test.cpp	GoogleTest unit tests (30 tests)
tests/script_test.cpp	Script interpreter tests (23 tests)
demos/sample.dtxt	Example script: draws shapes and exports SVG
demos/undo_demo.dtxt	Example script: 3 lines + undo = 2 in output
docs/feature-tour.svg	Visual walkthrough of the UI and tools

Build

Prerequisites

• C++17 compiler
• CMake 3.14+
• OpenGL + GLU + GLUT (or FreeGLUT)

Build and Run

cmake -B build
cmake --build build
./build/drawtool

The program prompts for line width on startup, then opens the drawing window.

Run Tests

ctest --test-dir build --output-on-failure

Platform Notes

• macOS: Uses -framework OpenGL -framework GLUT. Deprecated GLUT warnings are suppressed.
• Linux: Install FreeGLUT (sudo apt install freeglut3-dev).
• Windows: Link against opengl32.lib, glu32.lib, freeglut.lib.

Architecture

The application uses a shape-based data model (std::vector<Shape> g_shapes). All tools push shapes into this vector on mouse-up. The display callback clears the screen, re-renders all shapes sorted by layer, draws a rubber-band preview for the active tool, and overlays the HUD. This replaced the original direct-to-framebuffer approach and enables undo/redo, selection, export, and layer sorting.

State is encapsulated in the DrawingApp singleton, accessed via DrawingApp::instance(). GLUT callbacks delegate to this instance.

Dear ImGui

ImGui integration was evaluated for Tier 3. Given the legacy OpenGL + GLUT architecture, a full ImGui rewrite would require replacing the GLUT event loop or adding a compatibility shim. Instead, the HUD overlay provides the essential status display (tool, color, shape count, layer) natively. ImGui integration is a candidate for a future version using GLFW + OpenGL 3.3.

License

MIT

Security

See SECURITY.md for vulnerability reporting guidelines.