Dart Documentationbox2dViewportTransform

ViewportTransform class

class ViewportTransform {
 ViewportTransform(Vector2 e, Vector2 c, double s) :
   extents = new Vector2.copy(e),
   center = new Vector2.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.
  */
 Vector2 extents;

 /**
  * Returns the scaling factor used in converting from world sizes to rendering
  * sizes.
  */
 double scale;

 /**
  * center of the viewport.
  */
 Vector2 center;

 /**
  * Sets the transform's center to the given x and y coordinates,
  * and using the given scale.
  */
 void setCamera(double x, double y, double s) {
   center.setValues(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).
  */
 Vector2 get translation {
   Vector2 result = new Vector2.copy(extents);
   result.sub(center);
   return result;
 }

 void set translation(Vector2 translation) {
   center.setFrom(extents);
   center.sub(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(Vector2 argWorld, Vector2 argScreen) {
   // Correct for canvas considering the upper-left corner, rather than the
   // center, to be the origin.
   double gridCorrectedX = (argWorld.x * scale) + extents.x;
   double gridCorrectedY = extents.y - (argWorld.y * scale);

   argScreen.setValues(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(Vector2 argScreen, Vector2 argWorld) {
   double translationCorrectedX = argScreen.x - translation.x;
   double translationCorrectedY = argScreen.y + translation.y;

   double gridCorrectedX = (translationCorrectedX - extents.x) / scale;
   double gridCorrectedY = ((translationCorrectedY - extents.y) * -1) / scale;
   argWorld.setValues(gridCorrectedX, gridCorrectedY);
 }
}

Constructors

new ViewportTransform(Vector2 e, Vector2 c, double s) #

ViewportTransform(Vector2 e, Vector2 c, double s) :
 extents = new Vector2.copy(e),
 center = new Vector2.copy(c),
 scale = s;

Properties

Vector2 center #

center of the viewport.

Vector2 center

Vector2 extents #

This is the half-width and half-height. This should be the actual half-width and half-height, not anything transformed or scaled.

Vector2 extents

double scale #

Returns the scaling factor used in converting from world sizes to rendering sizes.

double scale

Vector2 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).

Vector2 get translation {
 Vector2 result = new Vector2.copy(extents);
 result.sub(center);
 return result;
}
void set translation(Vector2 translation) {
 center.setFrom(extents);
 center.sub(translation);
}

bool yFlip #

if we flip the y axis when transforming.

bool yFlip

Methods

void getScreenToWorld(Vector2 argScreen, Vector2 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(Vector2 argScreen, Vector2 argWorld) {
 double translationCorrectedX = argScreen.x - translation.x;
 double translationCorrectedY = argScreen.y + translation.y;

 double gridCorrectedX = (translationCorrectedX - extents.x) / scale;
 double gridCorrectedY = ((translationCorrectedY - extents.y) * -1) / scale;
 argWorld.setValues(gridCorrectedX, gridCorrectedY);
}

void getWorldToScreen(Vector2 argWorld, Vector2 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(Vector2 argWorld, Vector2 argScreen) {
 // Correct for canvas considering the upper-left corner, rather than the
 // center, to be the origin.
 double gridCorrectedX = (argWorld.x * scale) + extents.x;
 double gridCorrectedY = extents.y - (argWorld.y * scale);

 argScreen.setValues(gridCorrectedX + translation.x, gridCorrectedY +
     -translation.y);
}

void setCamera(double x, double y, double s) #

Sets the transform's center to the given x and y coordinates, and using the given scale.

void setCamera(double x, double y, double s) {
 center.setValues(x, y);
 scale = s;
}