Simplify modifier skeleton

@@ -0,0 +90,4 @@
+  switch (mmd.mode) {
+    case MOD_GREASE_PENCIL_SIMPLIFY_FIXED: {
+      for (int i = 0; i < mmd.step; i++) {
+

@@ -0,0 +102,4 @@
+    }
+    case MOD_GREASE_PENCIL_SIMPLIFY_SAMPLE: {
+      //geometry::resample_to_length(drawing.strokes(),field_context,
+      //BKE_gpencil_stroke_sample(gpd, gps, mmd->length, false, mmd->sharp_threshold);

@@ -0,0 +106,4 @@
+      break;
+    }
+    case MOD_GREASE_PENCIL_SIMPLIFY_MERGE: {
+      //BKE_gpencil_stroke_merge_distance(gpd, gpf, gps, mmd->distance, true);

@@ -0,0 +80,4 @@
+                              bke::greasepencil::Drawing &drawing)
+{
+  IndexMaskMemory memory;
+  bke::CurvesGeometry curves = drawing.strokes_for_write();

@@ -0,0 +94,4 @@
+        const OffsetIndices points_by_curve = curves.points_by_curve();
+        Array<int> target_count(curves.curves_num());
+        strokes.foreach_index(GrainSize(4096), [&](const int i) {
+          target_count[i] = math::round(float(points_by_curve[i].size()) / 2.0f + 0.5);

@@ -0,0 +92,4 @@
+    case MOD_GREASE_PENCIL_SIMPLIFY_FIXED: {
+      const OffsetIndices points_by_curve = curves.points_by_curve();
+      Array<int> target_count(curves.curves_num());
+      target_count.fill(2);

@@ -0,0 +245,4 @@
+          for (const int dst_point_i : range) {
+            /* Create a separate mixer for every point to avoid allocating temporary buffers
+             * in the mixer the size of the result curves and to improve memory locality. */
+            bke::attribute_math::DefaultMixer<T> mixer{dst_attribute.span.slice(dst_point_i, 1)};