Make vertial zooming faster and also framerate-independent.

client/config.js

@@ -6,6 +6,8 @@ const config = {
     ws_reconnect_timeout: 2000,
     brush_preview_timeout: 1000,
     second_finger_timeout: 500,
+    animation_decay: 16,
+    vertical_zoom_speed_multiplier: 3,
     debug_print: false,
     draw_bvh: false,
     draw_fullnodes: false,

client/webgl_draw.js

@@ -641,7 +641,11 @@ function exp_decay(a, b, decay, dt) {
 }
 
 function update_canvas_zoom(state, current, target, dt) {
-    const decay = 16;
+    let decay = config.animation_decay;
+
+    if (state.zoomdown) {
+        decay *= config.vertical_zoom_speed_multiplier; // to make it feel more responsive at fast speed
+    }
 
     if (Math.abs(1.0 - current / target) > 0.01) {
         state.canvas.zoom = exp_decay(state.canvas.zoom, target, decay, dt / 1000.0);

client/webgl_listeners.js

@@ -368,18 +368,8 @@ function pointermove(e, state, context) {
     }
 
     if (state.zooming) {
-        const zooming_in = e.movementY > 0;
-        const zooming_out = e.movementY < 0;
-
-        let zoom_level = null;
-
-        if (zooming_in) {
-            zoom_level = state.canvas.zoom_level + 1
-        } else if (zooming_out) {
-            zoom_level = state.canvas.zoom_level - 1;
-        } else {
-            return;
-        }
+        const zoom_level_increment = Math.round(Math.sign(e.movementY) * Math.sqrt(Math.abs(e.movementY)));
+        let zoom_level = state.canvas.zoom_level + zoom_level_increment;
 
         if (zoom_level < config.min_zoom_level || zoom_level > config.max_zoom_level) {
             return;