add stroke/pressure sensitivity to freedraw

packages/element/src/newElement.ts

@@ -445,6 +445,7 @@ export const newFreeDrawElement = (
     points?: ExcalidrawFreeDrawElement["points"];
     simulatePressure: boolean;
     pressures?: ExcalidrawFreeDrawElement["pressures"];
+    pressureSensitivity?: ExcalidrawFreeDrawElement["pressureSensitivity"];
   } & ElementConstructorOpts,
 ): NonDeleted<ExcalidrawFreeDrawElement> => {
   return {
@@ -453,6 +454,7 @@ export const newFreeDrawElement = (
     pressures: opts.pressures || [],
     simulatePressure: opts.simulatePressure,
     lastCommittedPoint: null,
+    pressureSensitivity: opts.pressureSensitivity ?? 1,
   };
 };
 

packages/element/src/renderElement.ts

@@ -1041,11 +1041,14 @@ export function getFreeDrawSvgPath(element: ExcalidrawFreeDrawElement) {
     ? element.points.map(([x, y], i) => [x, y, element.pressures[i]])
     : [[0, 0, 0.5]];
 
+  const sensitivity = element.pressureSensitivity;
+
   // Consider changing the options for simulated pressure vs real pressure
   const options: StrokeOptions = {
     simulatePressure: element.simulatePressure,
-    size: element.strokeWidth * 4.25,
-    thinning: 0.6,
+    // if sensitivity is not set, times 4.25 for backwards compatibility
+    size: element.strokeWidth * (sensitivity !== null ? 1 : 4.25),
+    thinning: 0.6 * (sensitivity ?? 1),
     smoothing: 0.5,
     streamline: 0.5,
     easing: (t) => Math.sin((t * Math.PI) / 2), // https://easings.net/#easeOutSine

packages/element/src/types.ts

@@ -377,6 +377,7 @@ export type ExcalidrawFreeDrawElement = _ExcalidrawElementBase &
     type: "freedraw";
     points: readonly LocalPoint[];
     pressures: readonly number[];
+    pressureSensitivity: number | null;
     simulatePressure: boolean;
     lastCommittedPoint: LocalPoint | null;
   }>;

packages/excalidraw/data/restore.ts

@@ -302,6 +302,7 @@ const restoreElement = (
         lastCommittedPoint: null,
         simulatePressure: element.simulatePressure,
         pressures: element.pressures,
+        pressureSensitivity: element.pressureSensitivity ?? null,
       });
     }
     case "image":