Dart Documentationbox2dIViewportTransform

IViewportTransform class

class IViewportTransform {
 IViewportTransform(Vector e, Vector c, num s) :
   extents = new Vector.copy(e),
   center = new Vector.copy(c),
   scale = s;

 /**
  * if we flip the y axis when transforming.
  */
 bool yFlip;

 /**
  * 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;

 /**
  * Returns the scaling factor used in converting from world sizes to rendering
  * sizes.
  */
 num scale;
 
 /**
  * center of the viewport.
  */
 Vector center;

 /**
  * 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;
 }
 /**
  * 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);
 }


 /**
  * 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);
 }

 /**
  * 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);
 }
}

Subclasses

CanvasViewportTransform

Constructors

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;

Properties

Vector center #

center

Vector extents #

extents

num scale #

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);
}

bool yFlip #

yFlip

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;
}