Tests: Add a simple LibGL render-test

At the moment we just check if we *can* render a simple triangle, we do
not yet actually test if the image is indeed the triangle we wanted.

This test also outputs the rendered image when GL_DEBUG is enabled to a
file called "picture.bmp" for manual verification.

Co-authored-by: sunverwerth <s.unverwerth@serenityos.org>

Meta/Lagom/CMakeLists.txt

@@ -520,6 +520,12 @@ if (BUILD_LAGOM)
             lagom_test(${source} LIBS LagomCompress)
         endforeach()
 
+        # GL
+        file(GLOB LIBGL_TESTS CONFIGURE_DEPENDS "../../Tests/LibGL/*.cpp")
+        foreach(source ${LIBGL_TESTS})
+            lagom_test(${source} LIBS LagomGL)
+        endforeach()
+
         # Regex
         file(GLOB LIBREGEX_TESTS CONFIGURE_DEPENDS "../../Tests/LibRegex/*.cpp")
         # RegexLibC test POSIX <regex.h> and contains many Serenity extensions

Tests/CMakeLists.txt

@@ -6,6 +6,7 @@ add_subdirectory(LibCore)
 add_subdirectory(LibCpp)
 add_subdirectory(LibELF)
 add_subdirectory(LibGfx)
+add_subdirectory(LibGL)
 add_subdirectory(LibIMAP)
 add_subdirectory(LibJS)
 add_subdirectory(LibM)

Tests/LibGL/CMakeLists.txt

@@ -0,0 +1,7 @@
+set(TEST_SOURCES
+    TestRender.cpp
+)
+
+foreach(source IN LISTS TEST_SOURCES)
+    serenity_test("${source}" LibGL LIBS LibGL)
+endforeach()

Tests/LibGL/TestRender.cpp

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2021, Leon Albrecht <leon2002.la@gmail.com>.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+
+#include <AK/Debug.h>
+#include <AK/Format.h>
+#include <LibGL/GL/gl.h>
+#include <LibGL/GLContext.h>
+#include <LibGfx/BMPWriter.h>
+#include <LibGfx/Bitmap.h>
+#include <LibGfx/FontDatabase.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#define RENDER_WIDTH 16
+#define RENDER_HEIGHT 16
+
+TEST_CASE(simple_triangle)
+{
+    auto bitmap = MUST(Gfx::Bitmap::try_create(Gfx::BitmapFormat::BGRx8888, { RENDER_WIDTH, RENDER_HEIGHT }));
+    auto context = GL::create_context(*bitmap);
+
+    GL::make_context_current(context);
+
+    glFrontFace(GL_CCW);
+    glCullFace(GL_BACK);
+    glEnable(GL_CULL_FACE);
+    glEnable(GL_DEPTH_TEST);
+
+    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+    glClearDepth(1.0);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+    glBegin(GL_TRIANGLES);
+    glColor4f(1, 1, 1, 1);
+    glVertex2f(0, 1);
+    glVertex2f(-1, -1);
+    glVertex2f(1, -1);
+    glEnd();
+
+    context->present();
+
+    EXPECT_EQ(glGetError(), 0u);
+    // FIXME: Verify that the image is indeed correct
+
+    if constexpr (GL_DEBUG) {
+        // output the image to manually verify that the output is correct
+        Gfx::BMPWriter writer {};
+        auto buffer = writer.dump(bitmap);
+        int fd = open("./picture.bmp", O_CREAT | O_WRONLY, 0755);
+        EXPECT(fd > 0);
+        ssize_t nwritten = write(fd, buffer.data(), buffer.size());
+        EXPECT_EQ((size_t)nwritten, buffer.size());
+        close(fd);
+    }
+}