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Sync LWJGL backends with ImGui upstream (OpenGL3 + GLFW) #391

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Merged
SpaiR merged 2 commits into from
Apr 25, 2026
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Merged

Sync LWJGL backends with ImGui upstream (OpenGL3 + GLFW) #391

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6f30afc
feat: synchronize GLFW with upstream imgui_impl_glfw.cpp (32f4c234)
SpaiR Apr 25, 2026
0411daf
feat: synchronize GL3 backend with upstream imgui_impl_opengl3.cpp (3…
SpaiR Apr 25, 2026
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106 changes: 86 additions & 20 deletions imgui-lwjgl3/src/main/java/imgui/gl3/ImGuiImplGl3.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,8 @@
import static org.lwjgl.opengl.GL20.glGetAttribLocation;
import static org.lwjgl.opengl.GL20.glGetProgramiv;
import static org.lwjgl.opengl.GL20.glGetUniformLocation;
import static org.lwjgl.opengl.GL21.GL_PIXEL_UNPACK_BUFFER;
import static org.lwjgl.opengl.GL21.GL_PIXEL_UNPACK_BUFFER_BINDING;
import static org.lwjgl.opengl.GL32.GL_ACTIVE_TEXTURE;
import static org.lwjgl.opengl.GL32.GL_ARRAY_BUFFER;
import static org.lwjgl.opengl.GL32.GL_ARRAY_BUFFER_BINDING;
Expand All @@ -34,6 +36,7 @@
import static org.lwjgl.opengl.GL32.GL_BLEND_EQUATION_RGB;
import static org.lwjgl.opengl.GL32.GL_BLEND_SRC_ALPHA;
import static org.lwjgl.opengl.GL32.GL_BLEND_SRC_RGB;
import static org.lwjgl.opengl.GL32.GL_CLAMP_TO_EDGE;
import static org.lwjgl.opengl.GL32.GL_COLOR_BUFFER_BIT;
import static org.lwjgl.opengl.GL32.GL_COMPILE_STATUS;
import static org.lwjgl.opengl.GL32.GL_CONTEXT_COMPATIBILITY_PROFILE_BIT;
Expand All @@ -53,6 +56,7 @@
import static org.lwjgl.opengl.GL32.GL_LINEAR;
import static org.lwjgl.opengl.GL32.GL_LINK_STATUS;
import static org.lwjgl.opengl.GL32.GL_MAJOR_VERSION;
import static org.lwjgl.opengl.GL32.GL_MAX_TEXTURE_SIZE;
import static org.lwjgl.opengl.GL32.GL_MINOR_VERSION;
import static org.lwjgl.opengl.GL32.GL_ONE;
import static org.lwjgl.opengl.GL32.GL_ONE_MINUS_SRC_ALPHA;
Expand All @@ -69,6 +73,8 @@
import static org.lwjgl.opengl.GL32.GL_TEXTURE_BINDING_2D;
import static org.lwjgl.opengl.GL32.GL_TEXTURE_MAG_FILTER;
import static org.lwjgl.opengl.GL32.GL_TEXTURE_MIN_FILTER;
import static org.lwjgl.opengl.GL32.GL_TEXTURE_WRAP_S;
import static org.lwjgl.opengl.GL32.GL_TEXTURE_WRAP_T;
import static org.lwjgl.opengl.GL32.GL_TRIANGLES;
import static org.lwjgl.opengl.GL32.GL_TRUE;
import static org.lwjgl.opengl.GL32.GL_UNPACK_ALIGNMENT;
Expand Down Expand Up @@ -135,7 +141,10 @@

/**
* This class is a straightforward port of the
* <a href="https://raw.githubusercontent.com/ocornut/imgui/1ee252772ae9c0a971d06257bb5c89f628fa696a/backends/imgui_impl_opengl3.cpp">imgui_impl_opengl3.cpp</a>.
* <a href="https://raw.githubusercontent.com/ocornut/imgui/32f4c234a8edd9a85b32a91c9e29afac15c50028/backends/imgui_impl_opengl3.cpp">imgui_impl_opengl3.cpp</a>.
* <p>
* The Java side mirrors the C++ file top-to-bottom — it is not a delta port, so reading the two files side-by-side
* is the easiest way to understand the structure here.
* <p>
* It does support a backup and restoring of the GL state in the same way the original Dear ImGui code does.
* Some of the very specific OpenGL variables may be ignored here,
Expand All @@ -156,9 +165,10 @@ public class ImGuiImplGl3 {
protected static class Data {
protected int glVersion = 0; // Extracted at runtime using GL_MAJOR_VERSION, GL_MINOR_VERSION queries (e.g. 320 for GL 3.2)
// protected boolean glProfileIsES2;
// protected boolean glProfileIsES3;
protected boolean glProfileIsES3;
protected boolean glProfileIsCompat;
protected int glProfileMask;
protected int maxTextureSize;
protected GLCapabilities glCapabilities = null;
protected String glslVersion = "";
protected int fontTexture = 0;
Expand All @@ -172,7 +182,8 @@ protected static class Data {
protected int elementsHandle = 0;
// protected int vertexBufferSize;
// protected int indexBufferSize;
// protected boolean hasPolygonMode;
protected boolean hasPolygonMode;
protected boolean hasBindSampler;
protected boolean hasClipOrigin;
}

Expand Down Expand Up @@ -275,8 +286,20 @@ public boolean init(final String glslVersion) {
}
}
data.glVersion = major * 100 + minor * 10;
data.glProfileMask = glGetInteger(GL_CONTEXT_PROFILE_MASK);
data.maxTextureSize = glGetInteger(GL_MAX_TEXTURE_SIZE);

// Some Mesa/EGL desktop drivers expose an ES3 context whose GL_VERSION starts with "OpenGL ES 3".
// Mirror upstream's runtime detection so the gates below match the C++ behavior on such configurations.
if (glVersion != null && glVersion.startsWith("OpenGL ES 3")) {
data.glProfileIsES3 = true;
}

// Upstream changelog 2023-06-20 (#6539): only query GL_CONTEXT_PROFILE_MASK on desktop GL >= 3.2.
if (!data.glProfileIsES3 && data.glVersion >= 320) {
data.glProfileMask = glGetInteger(GL_CONTEXT_PROFILE_MASK);
}
data.glProfileIsCompat = (data.glProfileMask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT) != 0;

if (data.glVersion < 330) { // Ignore in higher GL versions since they support sampler objects anyway
try {
data.glCapabilities = GL.getCapabilities();
Expand All @@ -293,9 +316,16 @@ public boolean init(final String glslVersion) {
io.addBackendFlags(ImGuiBackendFlags.RendererHasVtxOffset);
}

// In C++: io.BackendFlags |= ImGuiBackendFlags_RendererHasTextures — the renderer drives per-frame ImTextureData uploads.
// In Java: ImTextureData is not exposed in imgui-binding yet, so we keep the legacy createFontsTexture path
// and intentionally do not advertise the flag (follow-up: expose ImTextureData in the binding).

// We can create multi-viewports on the Renderer side (optional)
io.addBackendFlags(ImGuiBackendFlags.RendererHasViewports);

// In C++: platform_io.Renderer_TextureMaxWidth = platform_io.Renderer_TextureMaxHeight = bd->MaxTextureSize.
// In Java: setters are not exposed on ImGuiPlatformIO in imgui-binding (follow-up). data.maxTextureSize is queried above for parity.

if (glslVersion == null) {
if (IS_APPLE) {
data.glslVersion = "#version 150";
Expand All @@ -313,7 +343,12 @@ public boolean init(final String glslVersion) {
glGetIntegerv(GL_TEXTURE_BINDING_2D, currentTexture);
}

// Detect extensions we support
data.hasPolygonMode = !data.glProfileIsES3; // ES2 cannot occur in this binding (desktop GL only).
data.hasBindSampler = data.glVersion >= 330 || data.glProfileIsES3;
data.hasClipOrigin = data.glVersion >= 450;
// In C++: scans GL_NUM_EXTENSIONS for "GL_ARB_clip_control" to also enable hasClipOrigin on pre-4.5 contexts.
// In Java: omitted to avoid behavior drift versus the existing port (follow-up: honor the extension probe via glGetStringi).


if (ImGui.getIO().hasConfigFlags(ImGuiConfigFlags.ViewportsEnable)) {
Expand All @@ -330,6 +365,8 @@ public void shutdown() {
destroyDeviceObjects();

io.setBackendRendererName(null);
// In C++: io.BackendFlags also clears RendererHasTextures, then platform_io.ClearRendererHandlers() runs.
// In Java: RendererHasTextures is never set (see init), and ClearRendererHandlers is not exposed in imgui-binding (follow-up).
io.removeBackendFlags(ImGuiBackendFlags.RendererHasVtxOffset | ImGuiBackendFlags.RendererHasViewports);
data = null;
}
Expand All @@ -353,10 +390,10 @@ protected void setupRenderState(final ImDrawData drawData, final int fbWidth, fi
glDisable(GL_STENCIL_TEST);
glEnable(GL_SCISSOR_TEST);

if (data.glVersion >= 310) {
if (!data.glProfileIsES3 && data.glVersion >= 310) {
glDisable(GL_PRIMITIVE_RESTART);
}
if (data.glVersion >= 200) {
if (data.hasPolygonMode) {
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
}

Expand Down Expand Up @@ -397,8 +434,8 @@ protected void setupRenderState(final ImDrawData drawData, final int fbWidth, fi
glUniform1i(data.attribLocationTex, 0);
glUniformMatrix4fv(data.attribLocationProjMtx, false, props.orthoProjMatrix);

if (data.glVersion >= 330 || (data.glCapabilities != null && data.glCapabilities.GL_ARB_sampler_objects)) {
glBindSampler(0, 0);
if (data.hasBindSampler) {
glBindSampler(0, 0); // We use combined texture/sampler state. Applications using GL 3.3 and GL ES 3.0 may set that otherwise.
}

glBindVertexArray(gVertexArrayObject);
Expand Down Expand Up @@ -433,16 +470,20 @@ public void renderDrawData(final ImDrawData drawData) {
return;
}

// In C++: iterates draw_data->Textures and calls ImGui_ImplOpenGL3_UpdateTexture for each non-OK status.
// In Java: ImTextureData is not exposed in imgui-binding (follow-up); we keep the legacy createFontsTexture
// path triggered from newFrame(), so dynamic atlas updates are not honored here yet.

glGetIntegerv(GL_ACTIVE_TEXTURE, props.lastActiveTexture);
glActiveTexture(GL_TEXTURE0);
glGetIntegerv(GL_CURRENT_PROGRAM, props.lastProgram);
glGetIntegerv(GL_TEXTURE_BINDING_2D, props.lastTexture);
if (data.glVersion >= 330 || (data.glCapabilities != null && data.glCapabilities.GL_ARB_sampler_objects)) {
if (data.hasBindSampler) {
glGetIntegerv(GL_SAMPLER_BINDING, props.lastSampler);
}
glGetIntegerv(GL_ARRAY_BUFFER_BINDING, props.lastArrayBuffer);
glGetIntegerv(GL_VERTEX_ARRAY_BINDING, props.lastVertexArrayObject);
if (data.glVersion >= 200) {
if (data.hasPolygonMode) {
glGetIntegerv(GL_POLYGON_MODE, props.lastPolygonMode);
}
glGetIntegerv(GL_VIEWPORT, props.lastViewport);
Expand All @@ -458,7 +499,7 @@ public void renderDrawData(final ImDrawData drawData) {
props.lastEnableDepthTest = glIsEnabled(GL_DEPTH_TEST);
props.lastEnableStencilTest = glIsEnabled(GL_STENCIL_TEST);
props.lastEnableScissorTest = glIsEnabled(GL_SCISSOR_TEST);
if (data.glVersion >= 310) {
if (!data.glProfileIsES3 && data.glVersion >= 310) {
props.lastEnablePrimitiveRestart = glIsEnabled(GL_PRIMITIVE_RESTART);
}

Expand Down Expand Up @@ -492,6 +533,8 @@ public void renderDrawData(final ImDrawData drawData) {
// glBufferSubData(GL_ARRAY_BUFFER, 0, drawData.getCmdListVtxBufferData(n));
// glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, drawData.getCmdListIdxBufferData(n));

// In C++: also has an UseBufferSubData branch (orphaning + glBufferSubData).
// In Java: upstream forces UseBufferSubData = false, so we mirror only the glBufferData path here.
glBufferData(GL_ARRAY_BUFFER, drawData.getCmdListVtxBufferData(n), GL_STREAM_DRAW);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, drawData.getCmdListIdxBufferData(n), GL_STREAM_DRAW);

Expand Down Expand Up @@ -541,7 +584,7 @@ public void renderDrawData(final ImDrawData drawData) {
glUseProgram(props.lastProgram[0]);
}
glBindTexture(GL_TEXTURE_2D, props.lastTexture[0]);
if (data.glVersion >= 330 || (data.glCapabilities != null && data.glCapabilities.GL_ARB_sampler_objects)) {
if (data.hasBindSampler) {
glBindSampler(0, props.lastSampler[0]);
}
glActiveTexture(props.lastActiveTexture[0]);
Expand All @@ -559,23 +602,28 @@ public void renderDrawData(final ImDrawData drawData) {
else glDisable(GL_STENCIL_TEST);
if (props.lastEnableScissorTest) glEnable(GL_SCISSOR_TEST);
else glDisable(GL_SCISSOR_TEST);
if (data.glVersion >= 310) {
if (!data.glProfileIsES3 && data.glVersion >= 310) {
if (props.lastEnablePrimitiveRestart) {
glEnable(GL_PRIMITIVE_RESTART);
} else {
glDisable(GL_PRIMITIVE_RESTART);
}
}
if (data.glVersion <= 310 || data.glProfileIsCompat) {
glPolygonMode(GL_FRONT, props.lastPolygonMode[0]);
glPolygonMode(GL_BACK, props.lastPolygonMode[1]);
} else {
glPolygonMode(GL_FRONT_AND_BACK, props.lastPolygonMode[0]);
// Desktop OpenGL 3.0 and OpenGL 3.1 had separate polygon draw modes for front-facing and back-facing faces of polygons
if (data.hasPolygonMode) {
if (data.glVersion <= 310 || data.glProfileIsCompat) {
glPolygonMode(GL_FRONT, props.lastPolygonMode[0]);
glPolygonMode(GL_BACK, props.lastPolygonMode[1]);
} else {
glPolygonMode(GL_FRONT_AND_BACK, props.lastPolygonMode[0]);
}
}
glViewport(props.lastViewport[0], props.lastViewport[1], props.lastViewport[2], props.lastViewport[3]);
glScissor(props.lastScissorBox[0], props.lastScissorBox[1], props.lastScissorBox[2], props.lastScissorBox[3]);
}

// In C++: the legacy CreateFontsTexture has been removed in favor of UpdateTexture(WantCreate), driven by ImGuiPlatformIO::Textures.
// In Java: ImTextureData is not exposed in imgui-binding yet, so we keep the legacy path here (follow-up: migrate once exposed).
public boolean createFontsTexture() {
final ImFontAtlas fontAtlas = ImGui.getIO().getFonts();

Expand All @@ -592,7 +640,9 @@ public boolean createFontsTexture() {
glBindTexture(GL_TEXTURE_2D, data.fontTexture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glPixelStorei(GL_UNPACK_ALIGNMENT, 4); // Not on WebGL/ES
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1); // Not on WebGL/ES
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0); // Not on WebGL/ES
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0); // Not on WebGL/ES
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0); // Not on WebGL/ES
Expand Down Expand Up @@ -660,9 +710,14 @@ protected boolean createDeviceObjects() {
// Backup GL state
final int[] lastTexture = new int[1];
final int[] lastArrayBuffer = new int[1];
final int[] lastPixelUnpackBuffer = new int[1];
final int[] lastVertexArray = new int[1];
glGetIntegerv(GL_TEXTURE_BINDING_2D, lastTexture);
glGetIntegerv(GL_ARRAY_BUFFER_BINDING, lastArrayBuffer);
if (data.glVersion >= 210) {
glGetIntegerv(GL_PIXEL_UNPACK_BUFFER_BINDING, lastPixelUnpackBuffer);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
}
glGetIntegerv(GL_VERTEX_ARRAY_BINDING, lastVertexArray);

final int glslVersionValue = parseGlslVersionString(data.glslVersion);
Expand Down Expand Up @@ -718,11 +773,17 @@ protected boolean createDeviceObjects() {
data.vboHandle = glGenBuffers();
data.elementsHandle = glGenBuffers();

// In C++: the font texture is now created lazily through ImGui_ImplOpenGL3_UpdateTexture(WantCreate),
// driven by the platform_io.Textures iteration in RenderDrawData.
// In Java: ImTextureData is not exposed in imgui-binding (follow-up); keep the legacy createFontsTexture call here.
createFontsTexture();

// Restore modified GL state
glBindTexture(GL_TEXTURE_2D, lastTexture[0]);
glBindBuffer(GL_ARRAY_BUFFER, lastArrayBuffer[0]);
if (data.glVersion >= 210) {
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, lastPixelUnpackBuffer[0]);
}
glBindVertexArray(lastVertexArray[0]);

return true;
Expand All @@ -741,6 +802,8 @@ public void destroyDeviceObjects() {
glDeleteProgram(data.shaderHandle);
data.shaderHandle = 0;
}
// In C++: iterates ImGui::GetPlatformIO().Textures and calls ImGui_ImplOpenGL3_DestroyTexture for each entry with RefCount == 1.
// In Java: ImTextureData is not exposed in imgui-binding (follow-up); we delete the legacy fontTexture directly.
destroyFontsTexture();
}

Expand All @@ -754,13 +817,16 @@ private final class RendererRenderWindowFunction extends ImPlatformFuncViewport
@Override
public void accept(final ImGuiViewport vp) {
if (!vp.hasFlags(ImGuiViewportFlags.NoRendererClear)) {
glClearColor(0, 0, 0, 0);
glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT);
}
renderDrawData(vp.getDrawData());
}
}

// In C++: renamed to ImGui_ImplOpenGL3_InitMultiViewportSupport / ShutdownMultiViewportSupport.
// In Java: kept the legacy initPlatformInterface / shutdownPlatformInterface names — they are protected and renaming
// would break subclasses that override the multi-viewport hook.
protected void initPlatformInterface() {
ImGui.getPlatformIO().setRendererRenderWindow(new RendererRenderWindowFunction());
}
Expand Down
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