Window resize

[Xaklse]

In case your SFML application isn't in fullscreen mode, if you resize the render window, the widgets become deformed and mouse input isn't handled correctly.

This is what I have in imgui-rendering-SFML.h (no pushGLStates/popGLStates and usage of glViewport, exactly as examples found in imgui):

namespace ImGui
{
    namespace ImImpl
    {
        static sf::RenderTarget* ImImpl_rtarget;
        static sf::Texture* ImImpl_fontTex;

        static void ImImpl_RenderDrawLists(ImDrawData* draw_data)
        {
            if (draw_data->CmdListsCount == 0)
                return;

            GLint last_texture;
            glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
            GLint last_viewport[4];
            glGetIntegerv(GL_VIEWPORT, last_viewport);
            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);

            ImGuiIO& io = ImGui::GetIO();
            glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
            glMatrixMode(GL_PROJECTION);
            glPushMatrix();
            glLoadIdentity();
            glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f);
            glMatrixMode(GL_MODELVIEW);
            glPushMatrix();
            glLoadIdentity();

            sf::RenderStates states;
            states.blendMode = sf::BlendMode(sf::BlendMode::SrcAlpha, sf::BlendMode::OneMinusSrcAlpha);

#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
            for (int n = 0; n < draw_data->CmdListsCount; n++)
            {
                const ImDrawList* cmd_list = draw_data->CmdLists[n];
                const unsigned char* vtx_buffer = (const unsigned char*)&cmd_list->VtxBuffer.front();
                const ImDrawIdx* idx_buffer = &cmd_list->IdxBuffer.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)));

                for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.size(); cmd_i++)
                {
                    const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
                    if (pcmd->UserCallback)
                    {
                        pcmd->UserCallback(cmd_list, pcmd);
                    }
                    else
                    {
                        sf::Vector2u win_size = ImImpl_rtarget->getSize();
                        sf::Texture::bind(ImImpl::ImImpl_fontTex);
                        glScissor((int)pcmd->ClipRect.x, (int)(win_size.y - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
                        glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer);
                    }
                    idx_buffer += pcmd->ElemCount;
                }
            }
#undef OFFSETOF

            // Restore modified state
            glDisableClientState(GL_COLOR_ARRAY);
            glDisableClientState(GL_TEXTURE_COORD_ARRAY);
            glDisableClientState(GL_VERTEX_ARRAY);
            glBindTexture(GL_TEXTURE_2D, last_texture);
            glMatrixMode(GL_MODELVIEW);
            glPopMatrix();
            glMatrixMode(GL_PROJECTION);
            glPopMatrix();
            glPopAttrib();
            glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
        }
    }

Hope this helps if you get this error.

[Mischa-Alff]

Is this an issue or a patch? If this is a patch, I'd appreciate it if you could please make a PR that fixes it. Thanks.

[Xaklse]

My apologies, this isn't a proper PR because I didn't clone the repository.
This code works for me with a very very basic WIP application, but someone else should test it, just to be sure this is a correct solution.

[codecat]

I'll take a look at this later tomorrow. Do you want me to turn this into a pull request for you, @Xaklse?

[codecat]

Hm, I don't see why this change is necessary, mouse input works fine for me when resizing without this change and nothing gets deformed..

[Xaklse]

I wonder what was wrong then... but I guess you're using now the most recent code with the newest PR accepted, right?

[codecat]

Yes.

[Xaklse]

I upgraded to latest version of imgui and imgui-backends, I got the same problem as before.
Something is fishy... could be something related to my code.
Regards

[codecat]

What happens if you take the example from #10? Does it still show the issues?

[codecat]

@Xaklse Can we re-open this issue? I finally figured out the exact problem you are describing, and you're right :)

[codecat]

@Xaklse This fix doesn't seem to work, unless I'm not applying it correctly. Was the only thing you added the glViewport calls?

[Xaklse]

I added the glViewport calls, exactly as in other imgui examples, and removed the calls to pushGLStates, popGLStates and resetGLStates.
It works for me, but might break something, I'm not using SFML to draw its stuff like Sprites.

[codecat]

The push/pop/reset should not be removed, see issue #10.

[James2022-rgb]

Am I correct in thinking this problem persists, seeing the last commit date ?
I'm looking to use imgui with SFML and just found this repo.