From c3f66d966c4613bb7531ec47b6344bfac8578b23 Mon Sep 17 00:00:00 2001
From: "A.Olokhtonov" <a.olokhtonov@norsi-trans.ru>
Date: Sat, 6 Apr 2024 13:57:40 +0300
Subject: [PATCH] Determinitstic zooming

---
 client/index.js           |  8 +++++---
 client/wasm/lod.c         |  2 --
 client/webgl_draw.js      |  5 +++--
 client/webgl_listeners.js | 33 +++++++++++++++++----------------
 4 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/client/index.js b/client/index.js
index 384b07c..c877b5e 100644
--- a/client/index.js
+++ b/client/index.js
@@ -13,8 +13,9 @@ const config = {
     second_finger_timeout: 500,
     buffer_first_touchmoves: 5,
     debug_print: false,
-    min_zoom: 0.00001,
-    max_zoom: 10,
+    zoom_delta: 0.15,
+    min_zoom_level: -75,
+    max_zoom_level: 20,
     initial_offline_timeout: 1000,
     default_color: 0x00,
     default_width: 8,
@@ -26,7 +27,7 @@ const config = {
     dynamic_stroke_texture_size: 128, // means no more than 128^2 = 16K dynamic strokes at once
     bvh_fullnode_depth: 5,
     benchmark: {
-        zoom: 0.00001,
+        zoom_level: -75,
         offset: { x: 425, y: -1195 },
         frames: 500,
     },
@@ -137,6 +138,7 @@ async function main() {
 
         'canvas': {
             'offset': { 'x': 0, 'y': 0 },
+            'zoom_level': 0,
             'zoom': 1.0,
         },
 
diff --git a/client/wasm/lod.c b/client/wasm/lod.c
index fd5508f..0e6ce43 100644
--- a/client/wasm/lod.c
+++ b/client/wasm/lod.c
@@ -1,5 +1,3 @@
-// clang -Oz --target=wasm32 -nostdlib -Wl,--export-all,--no-entry -msimd128 lod.c -o lod.wasm
-
 #include <wasm_simd128.h>
 
 extern char __heap_base;
diff --git a/client/webgl_draw.js b/client/webgl_draw.js
index 28247cc..78e79a4 100644
--- a/client/webgl_draw.js
+++ b/client/webgl_draw.js
@@ -195,8 +195,9 @@ async function draw(state, context) {
 
     document.getElementById('debug-stats').innerHTML = `
     <span>Segments onscreen: ${segment_count}</span>
-    <span>Canvas offset: (${state.canvas.offset.x}, ${state.canvas.offset.y})</span>
-    <span>Canvas zoom: ${Math.round(state.canvas.zoom * 100000) / 100000}</span>`;
+    <span>Canvas offset: (${Math.round(state.canvas.offset.x * 100) / 100}, ${Math.round(state.canvas.offset.y * 100) / 100})</span>
+    <span>Canvas zoom level: ${state.canvas.zoom_level}</span>
+    <span>Canvas zoom: ${Math.round(state.canvas.zoom * 100) / 100}</span>`;
 
     if (context.gpu_timer_ext) {
         gl.endQuery(context.gpu_timer_ext.TIME_ELAPSED_EXT);
diff --git a/client/webgl_listeners.js b/client/webgl_listeners.js
index 6848d4d..5f1247a 100644
--- a/client/webgl_listeners.js
+++ b/client/webgl_listeners.js
@@ -58,10 +58,13 @@ function debug_panel_init(state, context) {
     });
 
     document.getElementById('debug-begin-benchmark').addEventListener('click', (e) => {
-        state.canvas.zoom = config.benchmark.zoom;
+        state.canvas.zoom_level = config.benchmark.zoom_level;
         state.canvas.offset.x = config.benchmark.offset.x;
         state.canvas.offset.y = config.benchmark.offset.y;
 
+        const dz = (state.canvas.zoom_level > 0 ? config.zoom_delta : -config.zoom_delta);
+        state.canvas.zoom = Math.pow(1.0 + dz, Math.abs(state.canvas.zoom_level))
+
         state.debug.benchmark_mode = true;
 
         const origin_x = state.canvas.offset.x;
@@ -328,31 +331,29 @@ function wheel(e, state, context) {
     const screenp = {'x': window.devicePixelRatio * e.clientX, 'y': window.devicePixelRatio * e.clientY};
     const canvasp = screen_to_canvas(state, screenp);
 
-    const dz = (e.deltaY < 0 ? 0.1 : -0.1);
-    const old_zoom = state.canvas.zoom;
-
-    state.canvas.zoom *= (1.0 + dz);
+    const zooming_in = e.deltaY < 0;
+    const zoom_level = zooming_in ? state.canvas.zoom_level + 1 : state.canvas.zoom_level - 1;
 
-    if (state.canvas.zoom > config.max_zoom) {
-        state.canvas.zoom = old_zoom;
+    if (zoom_level < config.min_zoom_level || zoom_level > config.max_zoom_level) {
         return;
     }
 
-    if (state.canvas.zoom < config.min_zoom) {
-        state.canvas.zoom = old_zoom;
-        return;
-    }
+    state.canvas.zoom_level = zoom_level;
+
+    const dz = (zoom_level > 0 ? config.zoom_delta : -config.zoom_delta);
+    const old_zoom = state.canvas.zoom;
+    const new_zoom = Math.pow(1.0 + dz, Math.abs(zoom_level))
 
     // If we are moving our canvas, we don't need to follow anymore
     if (state.following_player !== null) {
         toggle_follow_player(state, state.following_player);
     }
-    
-    const zoom_offset_x = Math.round((dz * old_zoom) * canvasp.x);
-    const zoom_offset_y = Math.round((dz * old_zoom) * canvasp.y);
 
-    state.canvas.offset.x -= zoom_offset_x;
-    state.canvas.offset.y -= zoom_offset_y;
+    // https://gist.github.com/aolo2/a373363419bd5a9283977ab9f8841f78
+    state.canvas.offset.x = screenp.x - (screenp.x - state.canvas.offset.x) * new_zoom / old_zoom;
+    state.canvas.offset.y = screenp.y - (screenp.y - state.canvas.offset.y) * new_zoom / old_zoom;
+
+    state.canvas.zoom = new_zoom;
 
     fire_event(state, movecanvas_event(state));