add renderstate D3DRS_SHADEMODE for Dx9 impl

add backuping transform for Dx9 impl
(#1790, #1687)

examples/directx9_example/imgui_impl_dx9.cpp

@@ -76,6 +76,12 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
     if (g_pd3dDevice->CreateStateBlock(D3DSBT_ALL, &d3d9_state_block) < 0)
         return;
 
+    // Backup the DX9 transform
+    D3DMATRIX last_world, last_view, last_projection;
+    g_pd3dDevice->GetTransform(D3DTS_WORLD, &last_world);
+    g_pd3dDevice->GetTransform(D3DTS_VIEW, &last_view);
+    g_pd3dDevice->GetTransform(D3DTS_PROJECTION, &last_projection);
+
     // Copy and convert all vertices into a single contiguous buffer
     CUSTOMVERTEX* vtx_dst;
     ImDrawIdx* idx_dst;
@@ -116,7 +122,7 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
     vp.MaxZ = 1.0f;
     g_pd3dDevice->SetViewport(&vp);
 
-    // Setup render state: fixed-pipeline, alpha-blending, no face culling, no depth testing
+    // Setup render state: fixed-pipeline, alpha-blending, no face culling, no depth testing, shade mode (for gradient)
     g_pd3dDevice->SetPixelShader(NULL);
     g_pd3dDevice->SetVertexShader(NULL);
     g_pd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
@@ -128,6 +134,7 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
     g_pd3dDevice->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
     g_pd3dDevice->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
     g_pd3dDevice->SetRenderState(D3DRS_SCISSORTESTENABLE, true);
+    g_pd3dDevice->SetRenderState(D3DRS_SHADEMODE, D3DSHADE_GOURAUD);
     g_pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_MODULATE);
     g_pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
     g_pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
@@ -179,6 +186,11 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
         vtx_offset += cmd_list->VtxBuffer.Size;
     }
 
+    // Restore the DX9 transform
+    g_pd3dDevice->SetTransform(D3DTS_WORLD, &last_world);
+    g_pd3dDevice->SetTransform(D3DTS_VIEW, &last_view);
+    g_pd3dDevice->SetTransform(D3DTS_PROJECTION, &last_projection);
+
     // Restore the DX9 state
     d3d9_state_block->Apply();
     d3d9_state_block->Release();