Kotlin Desktop: Canvas, Path & Pointer Input Drawing App | Lesson 11
Build a freehand drawing app with Kotlin Compose Desktop! Learn how to use the Canvas composable, draw paths with moveTo/lineTo, apply smooth
stroke styles with StrokeCap.Round, and capture pointer input with detectDragGestures. Includes a color palette, adjustable stroke width, undo,
and clear.
What You'll Learn:
Canvas composable with DrawScope for custom 2D drawing
Path API with moveTo and lineTo for building freehand strokes
Stroke styles: StrokeCap.Round, StrokeJoin.Round for smooth lines
pointerInput modifier with detectDragGestures for gesture handling
mutableStateListOf for reactive stroke list management
Color palette with CircleShape selection indicators
Slider for adjustable stroke width
Undo (removeLast) and clear operations
Timestamps:
0:00 - Introduction
0:15 - Preview: What We're Building
0:45 - Project Setup (Gradle, Compose Dependencies)
2:14 - Stroke Model (DrawingStroke Data Class)
3:42 - Drawing Canvas (Canvas, Path, Pointer Input)
6:01 - Drawing App (Toolbar, State Management)
8:20 - Main & Compile
10:10 - Live Demo: Drawing App in Action
11:50 - Recap & Key Takeaways
12:50 - Thanks for Watching
Key Takeaways:
1. Canvas — Canvas composable gives you a DrawScope for custom 2D rendering
2. Path — Path.moveTo/lineTo builds shapes, drawPath renders them on the canvas
3. Stroke — StrokeCap.Round and StrokeJoin.Round create smooth freehand lines
4. Input — pointerInput with detectDragGestures captures freehand drawing gestures
5. Undo — mutableStateListOf with removeLast provides simple undo functionality
Previous Lesson:
Lesson 10: Drag & Drop
/ . .
Next Lesson:
Lesson 12: Animations (coming soon)
Tech Stack:
Kotlin 2.1, Compose Multiplatform 1.7.3, Material3
Canvas API, Pointer Input, DrawScope
Gradle 8.10, JVM 17+
Source Code: https://github.com/GoCelesteAI/kotlin...
Taught by CelesteAI
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#kotlin #compose #desktop #material3 #canvas #drawing #path #pointerInput #tutorial #programming