Name: sketch-tool
Rating: 92
Author: andrejvysny

When to Use

•Implementing new sketch drawing tool
•Following tool lifecycle pattern
•Integrating snap/constraint systems

Architecture

•Base class: src/core/sketch/tools/SketchTool.h
•Manager: src/core/sketch/tools/SketchToolManager.h/cpp
•Existing tools: LineTool, ArcTool, CircleTool, RectangleTool, EllipseTool, MirrorTool, TrimTool

State Machine

cpp

enum class State { Idle, FirstClick, Drawing };

•Idle → FirstClick (on first click)
•FirstClick → Drawing (multi-point tools) or Idle (two-click tools)
•ESC cancels, returns to Idle

Required Interface

cpp

class MyTool : public SketchTool {
    void onMousePress(const Vec2d& pos, Qt::MouseButton button) override;
    void onMouseMove(const Vec2d& pos) override;
    void onMouseRelease(const Vec2d& pos, Qt::MouseButton button) override;
    void onKeyPress(Qt::Key key) override;
    void cancel() override;
    void render(SketchRenderer& renderer) override;
    std::string name() const override;
};

Registration Steps

•Add enum to ToolType in SketchToolManager.h
•Add case in createTool() factory (SketchToolManager.cpp:216-236)
•Connect UI button in ContextToolbar

Key Patterns

Snap integration

cpp

Vec2d finalPos = getSnappedPos(cursorPos);
if (snapResult_.snapped && !snapResult_.pointId.empty()) {
    useExistingPointId = snapResult_.pointId;
}

Degenerate prevention

cpp

if (length < constants::MIN_GEOMETRY_SIZE) return;

Auto-constraint

cpp

auto constraints = autoConstrainer_->inferLineConstraints(...);
applyInferredConstraints(constraints, entityId);

Preview rendering

cpp

void render(SketchRenderer& renderer) override {
    if (state_ == State::FirstClick) {
        renderer.setPreviewLine(startPoint_, currentPoint_);
    }
}

Creation flag for signals

cpp

bool wasCreated() const { return created_; }
void clearCreatedFlag() { created_ = false; }

CRITICAL: Coordinate System

SketchPlane::XY() uses non-standard mapping:

•Sketch X → World Y+ (0,1,0)
•Sketch Y → World X- (-1,0,0)