From 215747635d9a1c3b68e91d5216a58d58e8f5605f Mon Sep 17 00:00:00 2001
From: ocornut <omarcornut@gmail.com>
Date: Thu, 13 Aug 2015 23:13:20 -0600
Subject: [PATCH] Examples: DirectX11: resizing buffers dynamically (#299)

---
 .../directx11_example/imgui_impl_dx11.cpp     | 59 ++++++++++---------
 examples/directx9_example/imgui_impl_dx9.cpp  |  6 +-
 2 files changed, 34 insertions(+), 31 deletions(-)

diff --git a/examples/directx11_example/imgui_impl_dx11.cpp b/examples/directx11_example/imgui_impl_dx11.cpp
index 2f23a0636..5c2c6bea6 100644
--- a/examples/directx11_example/imgui_impl_dx11.cpp
+++ b/examples/directx11_example/imgui_impl_dx11.cpp
@@ -29,8 +29,7 @@ static ID3D11SamplerState*      g_pFontSampler = NULL;
 static ID3D11ShaderResourceView*g_pFontTextureView = NULL;
 static ID3D11RasterizerState*   g_pRasterizerState = NULL;
 static ID3D11BlendState*        g_pBlendState = NULL;
-static int                      VERTEX_BUFFER_SIZE = 20000;     // TODO: Make buffers smaller and grow dynamically as needed.
-static int                      INDEX_BUFFER_SIZE = 40000;      // TODO: Make buffers smaller and grow dynamically as needed.
+static int                      g_VertexBufferSize = 5000, g_IndexBufferSize = 10000;
 
 struct VERTEX_CONSTANT_BUFFER
 {
@@ -42,6 +41,35 @@ struct VERTEX_CONSTANT_BUFFER
 // - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
 static void ImGui_ImplDX11_RenderDrawLists(ImDrawData* draw_data)
 {
+    // Create and grow vertex/index buffers if needed
+    if (!g_pVB || g_VertexBufferSize < draw_data->TotalVtxCount)
+    {
+        if (g_pVB) { g_pVB->Release(); g_pVB = NULL; }
+        g_VertexBufferSize = draw_data->TotalVtxCount + 5000;
+        D3D11_BUFFER_DESC desc;
+        memset(&desc, 0, sizeof(D3D11_BUFFER_DESC));
+        desc.Usage = D3D11_USAGE_DYNAMIC;
+        desc.ByteWidth = g_VertexBufferSize * sizeof(ImDrawVert);
+        desc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
+        desc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
+        desc.MiscFlags = 0;
+        if (g_pd3dDevice->CreateBuffer(&desc, NULL, &g_pVB) < 0)
+            return;
+    }
+    if (!g_pIB || g_IndexBufferSize < draw_data->TotalIdxCount)
+    {
+        if (g_pIB) { g_pIB->Release(); g_pIB = NULL; }
+        g_IndexBufferSize = draw_data->TotalIdxCount + 10000;
+        D3D11_BUFFER_DESC bufferDesc;
+        memset(&bufferDesc, 0, sizeof(D3D11_BUFFER_DESC));
+        bufferDesc.Usage = D3D11_USAGE_DYNAMIC;
+        bufferDesc.ByteWidth = g_IndexBufferSize * sizeof(ImDrawIdx);
+        bufferDesc.BindFlags = D3D11_BIND_INDEX_BUFFER;
+        bufferDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
+        if (g_pd3dDevice->CreateBuffer(&bufferDesc, NULL, &g_pIB) < 0)
+            return;
+    }
+
     // Copy and convert all vertices into a single contiguous buffer
     D3D11_MAPPED_SUBRESOURCE vtx_resource, idx_resource;
     if (g_pd3dDeviceContext->Map(g_pVB, 0, D3D11_MAP_WRITE_DISCARD, 0, &vtx_resource) != S_OK)
@@ -253,7 +281,7 @@ bool    ImGui_ImplDX11_CreateDeviceObjects()
 {
     if (!g_pd3dDevice)
         return false;
-    if (g_pVB)
+    if (g_pFontSampler)
         ImGui_ImplDX11_InvalidateDeviceObjects();
 
     // Create the vertex shader
@@ -366,31 +394,6 @@ bool    ImGui_ImplDX11_CreateDeviceObjects()
         g_pd3dDevice->CreateRasterizerState(&desc, &g_pRasterizerState);
     }
 
-    // Create the vertex buffer
-    {
-        D3D11_BUFFER_DESC desc;
-        memset(&desc, 0, sizeof(D3D11_BUFFER_DESC));
-        desc.Usage = D3D11_USAGE_DYNAMIC;
-        desc.ByteWidth = VERTEX_BUFFER_SIZE * sizeof(ImDrawVert);
-        desc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
-        desc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
-        desc.MiscFlags = 0;
-        if (g_pd3dDevice->CreateBuffer(&desc, NULL, &g_pVB) < 0)
-            return false;
-    }
-
-    // Create the index buffer
-    {
-        D3D11_BUFFER_DESC bufferDesc;
-        memset(&bufferDesc, 0, sizeof(D3D11_BUFFER_DESC));
-        bufferDesc.Usage = D3D11_USAGE_DYNAMIC;
-        bufferDesc.ByteWidth = INDEX_BUFFER_SIZE * sizeof(ImDrawIdx);
-        bufferDesc.BindFlags = D3D11_BIND_INDEX_BUFFER;
-        bufferDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
-        if (g_pd3dDevice->CreateBuffer(&bufferDesc, NULL, &g_pIB) < 0)
-            return false;
-    }
-
     ImGui_ImplDX11_CreateFontsTexture();
 
     return true;
diff --git a/examples/directx9_example/imgui_impl_dx9.cpp b/examples/directx9_example/imgui_impl_dx9.cpp
index 1ee091aba..63c1b044e 100644
--- a/examples/directx9_example/imgui_impl_dx9.cpp
+++ b/examples/directx9_example/imgui_impl_dx9.cpp
@@ -32,17 +32,17 @@ struct CUSTOMVERTEX
 // - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
 static void ImGui_ImplDX9_RenderDrawLists(ImDrawData* draw_data)
 {
-    // Grow buffers if needed
+    // Create and grow buffers if needed
     if (!g_pVB || g_VertexBufferSize < draw_data->TotalVtxCount)
     {
-        if (g_pVB) g_pVB->Release();
+        if (g_pVB) { g_pVB->Release(); g_pVB = NULL; }
         g_VertexBufferSize = draw_data->TotalVtxCount + 5000;
         if (g_pd3dDevice->CreateVertexBuffer(g_VertexBufferSize * sizeof(CUSTOMVERTEX), D3DUSAGE_DYNAMIC | D3DUSAGE_WRITEONLY, D3DFVF_CUSTOMVERTEX, D3DPOOL_DEFAULT, &g_pVB, NULL) < 0)
             return;
     }
     if (!g_pIB || g_IndexBufferSize < draw_data->TotalIdxCount)
     {
-        if (g_pIB) g_pIB->Release();
+        if (g_pIB) { g_pIB->Release(); g_pIB = NULL; }
         g_IndexBufferSize = draw_data->TotalIdxCount + 10000;
         if (g_pd3dDevice->CreateIndexBuffer(g_IndexBufferSize * sizeof(ImDrawIdx), D3DUSAGE_DYNAMIC | D3DUSAGE_WRITEONLY, D3DFMT_INDEX16, D3DPOOL_DEFAULT, &g_pIB, NULL) < 0)
             return;