implement graphical drag feedback for zooming

[mandelbrot.git] / xulapp / chrome / mandelbrot / content / mandelbrot.js

diff --git a/xulapp/chrome/mandelbrot/content/mandelbrot.js b/xulapp/chrome/mandelbrot/content/mandelbrot.js
index 788e198bd6059fba5259f21dce6bb6ab2b8b1a06..e4c7d9a77de84f7dcae94470317f5f3ac5b86319 100644 (file)
--- a/xulapp/chrome/mandelbrot/content/mandelbrot.js
+++ b/xulapp/chrome/mandelbrot/content/mandelbrot.js
@@ -401,18 +401,23 @@ function drawPoint(context, img_x, img_y, C, iterMax, algorithm) {
 /***** pure UI functions *****/
 
 var zoomstart;
 /***** pure UI functions *****/
 
 var zoomstart;

+var imgBackup;

 
 function mouseevent(etype, event) {
   let canvas = document.getElementById("mbrotImage");
 
 function mouseevent(etype, event) {
   let canvas = document.getElementById("mbrotImage");

+  let context = canvas.getContext("2d");

   switch (etype) {
     case 'down':
   switch (etype) {
     case 'down':

-      if (event.button == 0)
+      if (event.button == 0) {

         // left button - start dragzoom
         zoomstart = {x: event.clientX - canvas.offsetLeft,
                      y: event.clientY - canvas.offsetTop};
         // left button - start dragzoom
         zoomstart = {x: event.clientX - canvas.offsetLeft,
                      y: event.clientY - canvas.offsetTop};

+        imgBackup = context.getImageData(0, 0, canvas.width, canvas.height);
+      }

       break;
     case 'up':
       if (event.button == 0 && zoomstart) {
       break;
     case 'up':
       if (event.button == 0 && zoomstart) {

+        context.putImageData(imgBackup, 0, 0);

         let zoomend = {x: event.clientX - canvas.offsetLeft,
                        y: event.clientY - canvas.offsetTop};
 
         let zoomend = {x: event.clientX - canvas.offsetLeft,
                        y: event.clientY - canvas.offsetTop};
 


@@ -447,6 +452,15 @@ function mouseevent(etype, event) {
         }
       }
       zoomstart = undefined;
         }
       }
       zoomstart = undefined;

+      break;
+    case 'move':
+      if (event.button == 0 && zoomstart) {
+        context.putImageData(imgBackup, 0, 0);
+        context.strokeStyle = "rgb(255,255,31)";
+        context.strokeRect(zoomstart.x, zoomstart.y,
+                           event.clientX - canvas.offsetLeft - zoomstart.x,
+                           event.clientY - canvas.offsetTop - zoomstart.y);
+      }

     break;
   }
 }
     break;
   }
 }