CanvasViewportTransform class
class CanvasViewportTransform extends IViewportTransform { static const int DEFAULT_DRAWING_SCALE = 20; /** * Constructs a new viewport transform with the default scale. */ CanvasViewportTransform(Vector _extents, Vector _center) : super(_extents, _center, DEFAULT_DRAWING_SCALE) { yFlip = true; } /** * Sets the rendering context such that all drawing commands given in terms * of the world coordinate system will display correctly on the canvas screen. */ void updateTransformation(CanvasRenderingContext2D ctx) { // Clear all previous transformation. ctx.setTransform(1,0,0,1,0,0); // Translate to the center of the canvas screen. This will be considered the // actual origin. ctx.translate(extents.x, extents.y); // Translate to account for the currently applied translation. ctx.translate(translation.x, translation.y); // Scale everything according to the current scale and mirror the y-axis. ctx.scale(scale, -scale); } }
Extends
IViewportTransform > CanvasViewportTransform
Static Properties
const int DEFAULT_DRAWING_SCALE #
DEFAULT_DRAWING_SCALE = 20
Constructors
Properties
Vector translation #
The current translation is the difference in canvas units between the actual center of the canvas and the currently specified center. For example, if the actual canvas center is (5, 5) but the current center is (6, 6), the translation is (1, 1).
Vector get translation { Vector result = new Vector.copy(extents); result.subLocal(center); return result; }
void set translation(Vector translation) { center.setFrom(extents); center.subLocal(translation); }
Methods
void getScreenToWorld(Vector argScreen, Vector argWorld) #
Takes the screen coordinates (argScreen) and puts the corresponding world coordinates in argWorld. It should be safe to give the same object as both parameters.
void getScreenToWorld(Vector argScreen, Vector argWorld) { num translationCorrectedX = argScreen.x - translation.x; num translationCorrectedY = argScreen.y + translation.y; num gridCorrectedX = (translationCorrectedX - extents.x) / scale; num gridCorrectedY = ((translationCorrectedY - extents.y) * -1) / scale; argWorld.setCoords(gridCorrectedX, gridCorrectedY); }
void getWorldToScreen(Vector argWorld, Vector argScreen) #
Takes the world coordinate (argWorld) puts the corresponding screen coordinate in argScreen. It should be safe to give the same object as both parameters.
void getWorldToScreen(Vector argWorld, Vector argScreen) { // Correct for canvas considering the upper-left corner, rather than the // center, to be the origin. num gridCorrectedX = (argWorld.x * scale) + extents.x; num gridCorrectedY = extents.y - (argWorld.y * scale); argScreen.setCoords(gridCorrectedX + translation.x, gridCorrectedY + -translation.y); }
void setCamera(num x, num y, num s) #
Sets the transform's center to the given x and y coordinates, and using the given scale.
void setCamera(num x, num y, num s) { center.setCoords(x, y); scale = s; }
void updateTransformation(CanvasRenderingContext2D ctx) #
Sets the rendering context such that all drawing commands given in terms of the world coordinate system will display correctly on the canvas screen.
void updateTransformation(CanvasRenderingContext2D ctx) { // Clear all previous transformation. ctx.setTransform(1,0,0,1,0,0); // Translate to the center of the canvas screen. This will be considered the // actual origin. ctx.translate(extents.x, extents.y); // Translate to account for the currently applied translation. ctx.translate(translation.x, translation.y); // Scale everything according to the current scale and mirror the y-axis. ctx.scale(scale, -scale); }