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zoomable-canvas.js
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zoomable-canvas.js
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// shim layer with setTimeout fallback
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function( callback ){
window.setTimeout(callback, 1000 / 60);
};
})();
var ZTC = {}; // namespace (Zoomable Text Canvas)
ZTC.data = [{
x : 0,
y : 0,
z : 1,
t : 'Bürgerbeteiligung und Demokratie'
},{
x : 0,
y : 0,
z : 1,
t : ' Datenschutz'
},{
x : 0,
y : 0,
z : 1,
t : 'Privatsphäre'
},{
x : 0,
y : 0,
z : 1,
t : 'Netzpolitik'
},{
x : 0,
y : 0,
z : 1,
t : 'Urheberrecht'
},{
x : 70,
y : 15,
z : 16,
t : 'fantastic'
},{
x : 71.1,
y : 16.1,
z : 256,
t : 'world!'
}];
ZTC.currentString = {
text : ''
};
ZTC.init = function(){
var c = document.getElementById('c');
var ctx = this.context = c.getContext('2d');
ctx.font = '32px sans-serif';
ctx.textBaseline = 'top';
var vp = this.viewport = { // initial viewport
x : 0,
y : 0,
w : 800,
h : 600,
dx : 0,
dy : 0
};
// mouse events
var dd = false, x0, y0; // drag and drop
$(c).attr('tabindex', '0')
.bind('mousewheel', function(event, delta, deltaX, deltaY) {
// fixed point zoom
var zoom = Math.pow(1.1, -delta); // delta always 1/-1?
var x = event.clientX - c.offsetLeft, y = event.clientY - c.offsetTop;
ZTC.fpZoom(zoom, x, y);
}).bind('mousedown', function(event){
dd = true;
x0 = event.clientX;
y0 = event.clientY;
}).bind('mouseup', function(){
dd = false;
vp.x += vp.dx;
vp.y += vp.dy;
vp.dx = 0;
vp.dy = 0;
}).bind('mousemove', function(event){
ZTC.mouseX = event.clientX - c.offsetLeft;
ZTC.mouseY = event.clientY - c.offsetTop;
if(dd){
var zoom_abs = vp.h/600,
dx = (x0 - event.clientX) * zoom_abs,
dy = (y0 - event.clientY) * zoom_abs;
vp.dx = dx;
vp.dy = dy;
}
}).bind('keypress', function(event){
event.preventDefault();
if(event.keyCode !== 13){ // else -> return key
var c = String.fromCharCode(event.charCode);
ZTC.currentString = {
text : ZTC.currentString.text + c
};
} else {
if(ZTC.currentString.text){
var zoom = vp.h/600;
ZTC.data.push({
t : ZTC.currentString.text,
x : vp.x + ZTC.mouseX * zoom,
y : vp.y + ZTC.mouseY * zoom,
z : 1/zoom
});
}
// reset
ZTC.currentString = {
text : ''
};
}
});
};
ZTC.draw = function(){
// no 'this' in this function, it's called by requestAnimFrame
var ctx = ZTC.context, vp = ZTC.viewport;
ctx.clearRect(0, 0, 800, 600);
ctx.save();
var s = 600/vp.h;
ctx.scale(s, s);
ctx.translate(-vp.x - vp.dx, -vp.y - vp.dy);
ZTC.data.forEach(function(o){
var zh = o.z*vp.h;
if(30 < zh && zh < 6000){
ctx.save();
ctx.translate(o.x, o.y);
ctx.scale(1/o.z, 1/o.z);
ctx.globalAlpha = Math.max(0, Math.min( zh/30 - 1 , 1));
ctx.fillText(o.t, 0, 0);
ctx.restore();
}
});
ctx.restore();
// print the text being typed
if(ZTC.currentString.text){
ctx.globalAlpha = 1;
ctx.fillText(ZTC.currentString.text, ZTC.mouseX, ZTC.mouseY);
}
// next frame
requestAnimFrame(ZTC.draw);
};
ZTC.fpZoom = function(zoom, x, y){
var vp = this.viewport;
// convert fixed point in absolute coordinates
var zoom_abs = vp.h/600;
var x_abs = x * zoom_abs + vp.x;
var y_abs = y * zoom_abs + vp.y;
// update viewport
vp.w *= zoom;
vp.h *= zoom;
zoom_abs = vp.h/600;
vp.x = x_abs - x * zoom_abs;
vp.y = y_abs - y * zoom_abs;
};
window.onload = function(){
ZTC.init();
ZTC.draw();
};