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SFML projects / Re: [GUI] SFML backend for ImGui

« on: March 04, 2015, 01:50:11 pm »

Good work. Unfortunately for me the clipping problem really made it a no go in its current state...
So to solve that I replaced the ImImpl_RenderDrawLists with the one you get from ImGuis example OpenGl implementation but modified to work with SFML textures... If someone else wants to use it remember you need to link opengl32.lib(or whatever is the equivalent if you aren't using VS)...

#include <SFML/OpenGL.hpp>
[...]
static void ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
{
        if (cmd_lists_count == 0)
                return;

        ImImpl_window->pushGLStates();

        // We are using the OpenGL fixed pipeline to make the example code simpler to read!
        // A probable faster way to render would be to collate all vertices from all cmd_lists into a single vertex buffer.
        // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
        glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        glDisable(GL_CULL_FACE);
        glDisable(GL_DEPTH_TEST);
        glEnable(GL_SCISSOR_TEST);
        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_TEXTURE_COORD_ARRAY);
        glEnableClientState(GL_COLOR_ARRAY);
        glEnable(GL_TEXTURE_2D);

        // Setup orthographic projection matrix
        const float width = ImGui::GetIO().DisplaySize.x;
        const float height = ImGui::GetIO().DisplaySize.y;
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glOrtho(0.0f, width, height, 0.0f, -1.0f, +1.0f);
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();

        // Render command lists
        for (int n = 0; n < cmd_lists_count; n++)
        {
                const ImDrawList* cmd_list = cmd_lists[n];
                const unsigned char* vtx_buffer = (const unsigned char*)&cmd_list->vtx_buffer.front();
                glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, pos)));
                glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, uv)));
                glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, col)));

                int vtx_offset = 0;
                for (size_t cmd_i = 0; cmd_i < cmd_list->commands.size(); cmd_i++)
                {
                        const ImDrawCmd* pcmd = &cmd_list->commands[cmd_i];
                        sf::Texture::bind((sf::Texture*)pcmd->texture_id);
                        glScissor((int)pcmd->clip_rect.x, (int)(height - pcmd->clip_rect.w), (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
                        glDrawArrays(GL_TRIANGLES, vtx_offset, pcmd->vtx_count);
                        vtx_offset += pcmd->vtx_count;
                }
        }

        // Restore modified state
        glDisableClientState(GL_COLOR_ARRAY);
        glDisableClientState(GL_TEXTURE_COORD_ARRAY);
        glDisableClientState(GL_VERTEX_ARRAY);
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glPopAttrib();

        ImImpl_window->popGLStates();
}

There is probably a way so that you don't need to call push/popGLStates but I don't know OpenGL so I can't fix that...