CanvasViewportTransform class
Transform for drawing using a canvas context. Y-flip is permenantly set to true.
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
Constructors
Static Properties
const int DEFAULT_DRAWING_SCALE #
static const int DEFAULT_DRAWING_SCALE = 20;
Properties
Vector extents #
This is the half-width and half-height. This should be the actual half-width and half-height, not anything transformed or scaled.
Vector extents;
final Type runtimeType #
A representation of the runtime type of the object.
external Type get runtimeType;
num scale #
Returns the scaling factor used in converting from world sizes to rendering sizes.
num scale;
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); }
Operators
bool operator ==(other) #
The equality operator.
The default behavior for all Object
s is to return true if and
only if this
and
other are the same object.
If a subclass overrides the equality operator it should override
the hashCode
method as well to maintain consistency.
bool operator ==(other) => identical(this, other);
Methods
new CanvasViewportTransform(Vector _extents, Vector _center) #
Constructs a new viewport transform with the default scale.
CanvasViewportTransform(Vector _extents, Vector _center) : super(_extents, _center, DEFAULT_DRAWING_SCALE) { yFlip = true; }
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); }
int hashCode() #
Get a hash code for this object.
All objects have hash codes. Hash codes are guaranteed to be the
same for objects that are equal when compared using the equality
operator ==
. Other than that there are no guarantees about
the hash codes. They will not be consistent between runs and
there are no distribution guarantees.
If a subclass overrides hashCode
it should override the
equality operator as well to maintain consistency.
external int hashCode();
new IViewportTransform(Vector e, Vector c, num s) #
IViewportTransform(Vector e, Vector c, num s) : extents = new Vector.copy(e), center = new Vector.copy(c), scale = s;
noSuchMethod(String name, List args) #
noSuchMethod
is invoked when users invoke a non-existant method
on an object. The name of the method and the arguments of the
invocation are passed to noSuchMethod
. If noSuchMethod
returns a value, that value becomes the result of the original
invocation.
The default behavior of noSuchMethod
is to throw a
noSuchMethodError
.
external Dynamic noSuchMethod(String name, List args);
const Object() #
Creates a new Object
instance.
Object
instances have no meaningful state, and are only useful
through their identity. An Object
instance is equal to itself
only.
const Object();
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; }
String toString() #
Returns a string representation of this object.
external String toString();
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); }