From 0941ca5cda9ba31ea28c8b4f3688863efa7858ce Mon Sep 17 00:00:00 2001
From: griffi-gh <prasol258@gmail.com>
Date: Wed, 22 Nov 2023 20:26:44 +0100
Subject: [PATCH] fix crash, ui core multi-draw call

---
 kubi-ui/src/backend/glium.rs | 32 ++++++++++++++++++++------------
 kubi-ui/src/draw.rs          | 23 +++++++++++++++--------
 2 files changed, 35 insertions(+), 20 deletions(-)

diff --git a/kubi-ui/src/backend/glium.rs b/kubi-ui/src/backend/glium.rs
index 72041ba..d1ac903 100644
--- a/kubi-ui/src/backend/glium.rs
+++ b/kubi-ui/src/backend/glium.rs
@@ -30,11 +30,11 @@ impl From<UiVertex> for Vertex {
 implement_vertex!(Vertex, position, color);
 
 pub struct GliumUiRenderer {
-  pub program: glium::Program,
-  pub vertex_buffer: glium::VertexBuffer<Vertex>,
-  pub index_buffer: glium::IndexBuffer<u32>,
-  pub vertex_count: usize,
-  pub index_count: usize,
+  program: glium::Program,
+  vertex_buffer: glium::VertexBuffer<Vertex>,
+  index_buffer: glium::IndexBuffer<u32>,
+  vertex_count: usize,
+  index_count: usize,
 }
 
 impl GliumUiRenderer {
@@ -73,18 +73,26 @@ impl GliumUiRenderer {
 
   fn write_buffer_data(&mut self, vtx: &[Vertex], idx: &[u32]) {
     log::debug!("uploading {} vertices and {} indices", vtx.len(), idx.len());
-    self.ensure_buffer_size(vtx.len(), idx.len());
-    self.vertex_buffer.invalidate();
-    self.vertex_buffer.slice_mut(0..vtx.len()).unwrap().write(vtx);
+
     self.vertex_count = vtx.len();
-    self.index_buffer.invalidate();
-    self.index_buffer.slice_mut(0..idx.len()).unwrap().write(idx);
     self.index_count = idx.len();
+
+    self.vertex_buffer.invalidate();
+    self.index_buffer.invalidate();
+
+    if self.vertex_count == 0 || self.index_count == 0 {
+      return
+    }
+
+    self.ensure_buffer_size(vtx.len(), idx.len());
+    self.vertex_buffer.slice_mut(0..vtx.len()).unwrap().write(vtx);
+    self.index_buffer.slice_mut(0..idx.len()).unwrap().write(idx);
   }
 
   pub fn update(&mut self, plan: &UiDrawPlan) {
-    let data_vtx = &plan.vertices.iter().copied().map(Vertex::from).collect::<Vec<_>>();
-    let data_idx = &plan.indices;
+    assert!(plan.calls.len() == 1, "multiple draw calls not supported yet");
+    let data_vtx = &plan.calls[0].vertices.iter().copied().map(Vertex::from).collect::<Vec<_>>();
+    let data_idx = &plan.calls[0].indices;
     self.write_buffer_data(data_vtx, data_idx);
   }
 
diff --git a/kubi-ui/src/draw.rs b/kubi-ui/src/draw.rs
index c03b129..bc44cd2 100644
--- a/kubi-ui/src/draw.rs
+++ b/kubi-ui/src/draw.rs
@@ -34,20 +34,25 @@ pub struct UiVertex {
 }
 
 #[derive(Default)]
-pub struct UiDrawPlan {
+pub struct UiDrawCall {
   pub vertices: Vec<UiVertex>,
   pub indices: Vec<u32>,
 }
 
+#[derive(Default)]
+pub struct UiDrawPlan {
+  pub calls: Vec<UiDrawCall>
+}
+
 impl UiDrawPlan {
   pub fn build(calls: &UiDrawCommands) -> Self {
-    let mut plan = Self::default();
-    for call in &calls.commands {
-      match call {
+    let mut call = UiDrawCall::default();
+    for command in &calls.commands {
+      match command {
         UiDrawCommand::Rectangle { position, size, color } => {
-          let idx = plan.vertices.len() as u32;
-          plan.indices.extend([idx, idx + 1, idx + 2, idx, idx + 2, idx + 3]);
-          plan.vertices.extend([
+          let idx = call.vertices.len() as u32;
+          call.indices.extend([idx, idx + 1, idx + 2, idx, idx + 2, idx + 3]);
+          call.vertices.extend([
             UiVertex {
               position: *position,
               color: *color,
@@ -68,6 +73,8 @@ impl UiDrawPlan {
         }
       }
     }
-    plan
+    Self {
+      calls: vec![call]
+    }
   }
 }