Method UpdateClipRect

lib/imgui/imgui_draw.cpp:451–468

Our scheme may appears a bit unusual, basically we want the most-common calls AddLine AddRect etc. to not have to perform any check so we always have a command ready in the stack. The cost of figuring out if a new command has to be added or if we can merge is paid in those Update** functions only.

// Our scheme may appears a bit unusual, basically we want the most-common calls AddLine AddRect etc. to not have to perform any check so we always have a command ready in the stack.
// The cost of figuring out if a new command has to be added or if we can merge is paid in those Update** functions only.
void ImDrawList::UpdateClipRect()
{
    // If current command is used with different settings we need to add a new command
    const ImVec4 curr_clip_rect = GetCurrentClipRect();
    ImDrawCmd* curr_cmd = CmdBuffer.Size > 0 ? &CmdBuffer.Data[CmdBuffer.Size-1] : NULL;
    if (!curr_cmd || (curr_cmd->ElemCount != 0 && memcmp(&curr_cmd->ClipRect, &curr_clip_rect, sizeof(ImVec4)) != 0) || curr_cmd->UserCallback != NULL)
    {
        AddDrawCmd();
        return;
    }

    // Try to merge with previous command if it matches, else use current command
    ImDrawCmd* prev_cmd = CmdBuffer.Size > 1 ? curr_cmd - 1 : NULL;
    if (curr_cmd->ElemCount == 0 && prev_cmd && memcmp(&prev_cmd->ClipRect, &curr_clip_rect, sizeof(ImVec4)) == 0 && prev_cmd->TextureId == GetCurrentTextureId() && prev_cmd->UserCallback == NULL)
        CmdBuffer.pop_back();
    else
        curr_cmd->ClipRect = curr_clip_rect;
}

void ImDrawList::UpdateTextureID()
{