From a4cfaa542c38cf73058bac9ad944de5cde380987 Mon Sep 17 00:00:00 2001
From: Alejandro Alonso <alejandroalonsofernandez@gmail.com>
Date: Mon, 2 Dec 2024 12:03:37 +0100
Subject: [PATCH] :tada: Refactor memory managemnt for color linear gradient
 stops

---
 frontend/src/app/render_wasm/api.cljs | 40 +++++++++++++++++++++------
 render-wasm/src/main.rs               | 31 +++++++++++++++++----
 render-wasm/src/mem.rs                | 17 ++++++++++++
 3 files changed, 74 insertions(+), 14 deletions(-)
 create mode 100644 render-wasm/src/mem.rs

diff --git a/frontend/src/app/render_wasm/api.cljs b/frontend/src/app/render_wasm/api.cljs
index 52ee0e08a..65a5a7fc8 100644
--- a/frontend/src/app/render_wasm/api.cljs
+++ b/frontend/src/app/render_wasm/api.cljs
@@ -13,6 +13,7 @@
    [app.config :as cf]
    [app.render-wasm.helpers :as h]
    [app.util.functions :as fns]
+   [goog.object :as gobj]
    [promesa.core :as p]))
 
 (defonce internal-frame-id nil)
@@ -43,6 +44,17 @@
         ;; rgba >>> 0 so we have an unsigned representation
     (unsigned-bit-shift-right (bit-or (bit-shift-left a 24) rgb) 0)))
 
+(defn- rgba-bytes-from-hex
+  "Takes a hex color in #rrggbb format, and an opacity value from 0 to 1 and returns an array with its r g b a values"
+  [hex opacity]
+  (let [rgb (js/parseInt (subs hex 1) 16)
+        a (mth/floor (* (or opacity 1) 0xff))
+        ;; rgba >>> 0 so we have an unsigned representation
+        r (bit-shift-right rgb 16)
+        g (bit-and (bit-shift-right rgb 8) 255)
+        b (bit-and rgb 255)]
+    [r g b a]))
+
 (defn cancel-render
   []
   (when internal-frame-id
@@ -108,15 +120,25 @@
               (let [rgba (rgba-from-hex color opacity)]
                 (h/call internal-module "_add_shape_solid_fill" rgba)))
             (when (and (some? gradient)  (= (:type gradient) :linear))
-              (h/call internal-module "_add_shape_linear_fill"
-                      (:start-x gradient)
-                      (:start-y gradient)
-                      (:end-x gradient)
-                      (:end-y gradient)
-                      opacity)
-              (run! (fn [stop]
-                      (let [rgba (rgba-from-hex (:color stop) (:opacity stop))]
-                        (h/call internal-module "_add_shape_fill_stop" rgba (:offset stop)))) (:stops gradient)))))
+              (let [stops     (:stops gradient)
+                    n-stops   (count stops)
+                    mem-size  (* 5 n-stops)
+                    stops-ptr (h/call internal-module "_alloc_bytes" mem-size)
+                    heap      (gobj/get ^js internal-module "HEAPU8")
+                    mem       (js/Uint8Array. (.-buffer heap) stops-ptr mem-size)]
+                (h/call internal-module "_add_shape_linear_fill"
+                        (:start-x gradient)
+                        (:start-y gradient)
+                        (:end-x gradient)
+                        (:end-y gradient)
+                        opacity)
+                (.set mem (js/Uint8Array. (clj->js (flatten (map (fn [stop]
+                                                                   (let [[r g b a] (rgba-bytes-from-hex (:color stop) (:opacity stop))
+                                                                         offset (:offset stop)]
+                                                                     [r g b a (* 100 offset)]))
+                                                                 stops)))))
+
+                (h/call internal-module "_add_shape_fill_stops" stops-ptr n-stops)))))
         fills))
 
 (defn- translate-blend-mode
diff --git a/render-wasm/src/main.rs b/render-wasm/src/main.rs
index 476a4a1d3..80af60b9c 100644
--- a/render-wasm/src/main.rs
+++ b/render-wasm/src/main.rs
@@ -1,6 +1,7 @@
 mod debug;
 mod images;
 mod math;
+pub mod mem;
 mod render;
 mod shapes;
 mod state;
@@ -176,14 +177,34 @@ pub extern "C" fn add_shape_linear_fill(
     }
 }
 
+#[derive(Debug)]
+pub struct RawStopData {
+    color: [u8; 4],
+    offset: u8,
+}
+
 #[no_mangle]
-pub extern "C" fn add_shape_fill_stop(raw_color: u32, offset: f32) {
+pub extern "C" fn add_shape_fill_stops(ptr: *mut RawStopData, n_stops: i32) {
     let state = unsafe { STATE.as_mut() }.expect("got an invalid state pointer");
     if let Some(shape) = state.current_shape() {
-        let color = skia::Color::new(raw_color);
-        shape
-            .add_gradient_stop(color, offset)
-            .expect("got no fill or an invalid one");
+        unsafe {
+            let buf = Vec::<RawStopData>::from_raw_parts(ptr, n_stops as usize, n_stops as usize);
+            for raw_stop in buf.iter() {
+                let color = skia::Color::from_argb(
+                    raw_stop.color[3],
+                    raw_stop.color[0],
+                    raw_stop.color[1],
+                    raw_stop.color[2],
+                );
+                shape
+                    .add_gradient_stop(color, (raw_stop.offset as f32) / 100.)
+                    .expect("got no fill or an invalid one");
+            }
+            mem::free(
+                ptr as *mut u8,
+                n_stops as usize * std::mem::size_of::<RawStopData>(),
+            );
+        }
     }
 }
 
diff --git a/render-wasm/src/mem.rs b/render-wasm/src/mem.rs
new file mode 100644
index 000000000..fecd40758
--- /dev/null
+++ b/render-wasm/src/mem.rs
@@ -0,0 +1,17 @@
+#[no_mangle]
+pub extern "C" fn alloc_bytes(len: usize) -> *mut u8 {
+    // create a new mutable buffer with capacity `len`
+    let mut buf: Vec<u8> = Vec::with_capacity(len);
+    let ptr = buf.as_mut_ptr();
+    // take ownership of the memory block and ensure the its destructor is not
+    // called when the object goes out of scope at the end of the function
+    std::mem::forget(buf);
+    return ptr;
+}
+
+pub fn free(ptr: *mut u8, len: usize) {
+    unsafe {
+        let buf = Vec::<u8>::from_raw_parts(ptr, len, len);
+        std::mem::forget(buf);
+    }
+}