st/gui: Refactor a few OpenGL drawing code into helper

src/xrt/state_trackers/gui/CMakeLists.txt

@@ -8,6 +8,8 @@ add_library(
 	st_gui STATIC
 	gui_common.h
 	gui_imgui.h
+	gui_ogl.c
+	gui_ogl.h
 	gui_ogl_sink.c
 	gui_prober.c
 	gui_scene.cpp

src/xrt/state_trackers/gui/gui_ogl.c

@@ -0,0 +1,96 @@
+// Copyright 2019-2023, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  OpenGL helper functions for drawing GUI elements.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @author Moses Turner <moses@collabora.com>
+ * @ingroup gui
+ */
+
+#include "math/m_api.h"
+
+#include "gui_ogl.h"
+#include "gui_imgui.h"
+
+
+/*
+ *
+ * Helpers.
+ *
+ */
+
+static void
+get_uvs(ImVec2 *uv0, ImVec2 *uv1, bool rotate_180, bool flip_y)
+{
+	// Flip direction of y (x) if we are rotating.
+	float u0 = rotate_180 ? 1.f : 0.f;
+	float u1 = rotate_180 ? 0.f : 1.f;
+
+	// Flip direction of v (y) if either flip_y or rotate_180 is true.
+	float v0 = (rotate_180 ^ flip_y) ? 1.f : 0.f;
+	float v1 = (rotate_180 ^ flip_y) ? 0.f : 1.f;
+
+	// Note: We can't easily do 90 or 270-degree rotations: https://github.com/ocornut/imgui/issues/3267
+	*uv0 = (ImVec2){u0, v0};
+	*uv1 = (ImVec2){u1, v1};
+}
+
+
+/*
+ *
+ * 'Exported' functions.
+ *
+ */
+
+void
+gui_ogl_draw_image(uint32_t width, uint32_t height, uint32_t tex_id, float scale, bool rotate_180, bool flip_y)
+{
+	ImVec2 uv0, uv1;
+	get_uvs(&uv0, &uv1, rotate_180, flip_y);
+
+	// Need to go via ints to get integer steps.
+	int w = (float)width * scale;
+	int h = (float)height * scale;
+
+	ImVec2 size = {(float)w, (float)h};
+	ImVec4 white = {1, 1, 1, 1};
+	ImVec4 black = {0, 0, 0, 1};
+	ImTextureID id = (ImTextureID)(intptr_t)tex_id;
+
+	igImageBg(id, size, uv0, uv1, white, white, black);
+}
+
+void
+gui_ogl_draw_background(uint32_t width, uint32_t height, uint32_t tex_id, bool rotate_180, bool flip_y)
+{
+	ImVec2 uv0, uv1;
+	get_uvs(&uv0, &uv1, rotate_180, flip_y);
+
+	const ImU32 white = 0xffffffff;
+	ImTextureID id = (ImTextureID)(intptr_t)tex_id;
+
+	ImGuiIO *io = igGetIO();
+
+	float in_w = (float)width;
+	float in_h = (float)height;
+	float out_w = io->DisplaySize.x;
+	float out_h = io->DisplaySize.y;
+
+	float scale_w = (float)out_w / in_w; // 128 / 1280 = 0.1
+	float scale_h = (float)out_h / in_h; // 128 / 800 =  0.16
+
+	float scale = MIN(scale_w, scale_h); // 0.1
+
+	float inside_w = in_w * scale;
+	float inside_h = in_h * scale;
+
+	float translate_x = (out_w - inside_w) / 2; // Should be 0 for 1280x800
+	float translate_y = (out_h - inside_h) / 2; // Should be (1280 - 800) / 2 = 240
+
+	ImVec2 p_min = {translate_x, translate_y};
+	ImVec2 p_max = {translate_x + inside_w, translate_y + inside_h};
+
+	ImDrawList *bg = igGetBackgroundDrawList();
+	ImDrawList_AddImage(bg, id, p_min, p_max, uv0, uv1, white);
+}

src/xrt/state_trackers/gui/gui_ogl.h

@@ -0,0 +1,39 @@
+// Copyright 2019-2023, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  OpenGL helper functions for drawing GUI elements.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @ingroup gui
+ */
+
+#pragma once
+
+#include "xrt/xrt_compiler.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*!
+ * Draw the given textures as igImage, scale of 1.0f == 100%.
+ *
+ * @ingroup gui
+ */
+void
+gui_ogl_draw_image(uint32_t width, uint32_t height, uint32_t tex_id, float scale, bool rotate_180, bool flip_y);
+
+
+/*!
+ * Draw the given texture to the background of the current OS window.
+ *
+ * @ingroup gui
+ */
+void
+gui_ogl_draw_background(uint32_t width, uint32_t height, uint32_t tex_id, bool rotate_180, bool flip_y);
+
+
+#ifdef __cplusplus
+}
+#endif

src/xrt/state_trackers/gui/gui_scene_calibrate.c

@@ -27,6 +27,7 @@
 
 #include "gui_common.h"
 #include "gui_imgui.h"
+#include "gui_ogl.h"
 
 #include <assert.h>
 
@@ -134,15 +135,14 @@ draw_texture(struct gui_ogl_texture *tex, bool header)
 
 	gui_ogl_sink_update(tex);
 
-	int w = tex->w / (tex->half ? 2 : 1);
-	int h = tex->h / (tex->half ? 2 : 1);
+	gui_ogl_draw_image(          //
+	    (uint32_t)tex->w,        // width
+	    (uint32_t)tex->h,        // height
+	    tex->id,                 // tex_id
+	    tex->half ? 0.5f : 1.0f, // scale
+	    false,                   // rotate_180
+	    false);                  // flip_y
 
-	ImVec2 size = {(float)w, (float)h};
-	ImVec2 uv0 = {0, 0};
-	ImVec2 uv1 = {1, 1};
-	ImVec4 white = {1, 1, 1, 1};
-	ImTextureID id = (ImTextureID)(intptr_t)tex->id;
-	igImage(id, size, uv0, uv1, white, white);
 	igText("Sequence %u", (uint32_t)tex->seq);
 
 	char temp[512];

src/xrt/state_trackers/gui/gui_window_record.c

@@ -34,6 +34,7 @@
 #include "gstreamer/gst_pipeline.h"
 #endif
 
+#include "gui_ogl.h"
 #include "gui_imgui.h"
 #include "gui_common.h"
 #include "gui_window_record.h"
@@ -313,42 +314,12 @@ gui_window_record_to_background(struct gui_record_window *rw, struct gui_program
 
 	gui_ogl_sink_update(tex);
 
-	ImVec2 uv0 = {0, 0};
-	ImVec2 uv1 = {1, 1};
-
-	// Note: We can't easily do 90 or 270-degree rotations: https://github.com/ocornut/imgui/issues/3267
-	if (rw->texture.rotate_180) {
-		uv0 = (ImVec2){1, 1};
-		uv1 = (ImVec2){0, 0};
-	}
-
-	const ImU32 white = 0xffffffff;
-	ImTextureID id = (ImTextureID)(intptr_t)tex->id;
-
-	ImGuiIO *io = igGetIO();
-
-	// Shamelessly stolen from hg_model.cpp
-	float in_w = tex->w;
-	float in_h = tex->h;
-	float out_w = io->DisplaySize.x;
-	float out_h = io->DisplaySize.y;
-
-	float scale_w = (float)out_w / in_w; // 128 / 1280 = 0.1
-	float scale_h = (float)out_h / in_h; // 128 / 800 =  0.16
-
-	float scale = MIN(scale_w, scale_h); // 0.1
-
-	float inside_w = in_w * scale;
-	float inside_h = in_h * scale;
-
-	float translate_x = (out_w - inside_w) / 2; // Should be 0 for 1280x800
-	float translate_y = (out_h - inside_h) / 2; // Should be (1280 - 800) / 2 = 240
-
-	ImVec2 p_min = {translate_x, translate_y};
-	ImVec2 p_max = {translate_x + inside_w, translate_y + inside_h};
-
-	ImDrawList *bg = igGetBackgroundDrawList();
-	ImDrawList_AddImage(bg, id, p_min, p_max, uv0, uv1, white);
+	gui_ogl_draw_background(    //
+	    (uint32_t)tex->w,       // width
+	    (uint32_t)tex->h,       // height
+	    tex->id,                // tex_id
+	    rw->texture.rotate_180, // rotate_180
+	    false);                 // flip_y
 }
 
 void
@@ -363,22 +334,14 @@ gui_window_record_render(struct gui_record_window *rw, struct gui_program *p)
 
 	struct gui_ogl_texture *tex = rw->texture.ogl;
 
-	int w = tex->w * rw->texture.scale / 100.0f;
-	int h = tex->h * rw->texture.scale / 100.0f;
+	gui_ogl_draw_image(             //
+	    (uint32_t)tex->w,           // width
+	    (uint32_t)tex->h,           // height
+	    tex->id,                    // tex_id
+	    rw->texture.scale / 100.0f, // scale
+	    rw->texture.rotate_180,     // rotate_180
+	    false);                     // flip_y
 
-	ImVec2 size = {(float)w, (float)h};
-	ImVec2 uv0 = {0, 0};
-	ImVec2 uv1 = {1, 1};
-
-	// Note: We can't easily do 90 or 270-degree rotations: https://github.com/ocornut/imgui/issues/3267
-	if (rw->texture.rotate_180) {
-		uv0 = (ImVec2){1, 1};
-		uv1 = (ImVec2){0, 0};
-	}
-
-	ImVec4 white = {1, 1, 1, 1};
-	ImTextureID id = (ImTextureID)(intptr_t)tex->id;
-	igImage(id, size, uv0, uv1, white, white);
 
 #ifdef XRT_HAVE_GST
 	draw_gst(rw);