Dart Documentationbox2dViewportTransform

ViewportTransform class

class ViewportTransform {
 ViewportTransform(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);
 }
}

Constructors

new ViewportTransform(Vector e, Vector c, num s) #

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

Properties

Vector center #

center of the viewport.

Vector center

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

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);
}

bool yFlip #

if we flip the y axis when transforming.

bool 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;
}