[gnome-builder/wip/gtk4-port: 283/736] libide/gui: add recoloring helpers

[Christian Hergert <chergert src gnome org>]

commit 651681085fe241e826bcfa440f5c9ab2b011a969
Author: Christian Hergert <chergert redhat com>
Date:   Thu Mar 31 03:59:46 2022 -0700

    libide/gui: add recoloring helpers
    
    From text editor, to do the recoloring generation from schemes.

 src/libide/gui/ide-recoloring-private.h |  32 +++
 src/libide/gui/ide-recoloring.c         | 368 ++++++++++++++++++++++++++++++++
 src/libide/gui/meson.build              |   4 +
 3 files changed, 404 insertions(+)
---
diff --git a/src/libide/gui/ide-recoloring-private.h b/src/libide/gui/ide-recoloring-private.h
new file mode 100644
index 000000000..39e344fe8
--- /dev/null
+++ b/src/libide/gui/ide-recoloring-private.h
@@ -0,0 +1,32 @@
+/* ide-recoloring-private.h
+ *
+ * Copyright 2020 Christian Hergert <chergert redhat com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <gtksourceview/gtksource.h>
+
+G_BEGIN_DECLS
+
+char                 *_ide_recoloring_generate_css         (GtkSourceStyleScheme *style_scheme);
+gboolean              _ide_source_style_scheme_is_dark     (GtkSourceStyleScheme *style_scheme);
+GtkSourceStyleScheme *_ide_source_style_scheme_get_variant (GtkSourceStyleScheme *style_scheme,
+                                                            const char           *variant);
+
+G_END_DECLS
diff --git a/src/libide/gui/ide-recoloring.c b/src/libide/gui/ide-recoloring.c
new file mode 100644
index 000000000..ff2bbd485
--- /dev/null
+++ b/src/libide/gui/ide-recoloring.c
@@ -0,0 +1,368 @@
+/* ide-recoloring.c
+ *
+ * Copyright 2021 Christian Hergert <chergert redhat com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include "config.h"
+
+#include <math.h>
+
+#include "ide-recoloring-private.h"
+
+#define SHARED_CSS \
+  "@define-color card_fg_color @window_fg_color;\n" \
+  "@define-color headerbar_fg_color @window_fg_color;\n" \
+  "@define-color headerbar_border_color @window_fg_color;\n" \
+  "@define-color popover_fg_color @window_fg_color;\n" \
+  "@define-color dark_fill_bg_color @headerbar_bg_color;\n" \
+  "@define-color view_bg_color @card_bg_color;\n" \
+  "@define-color view_fg_color @window_fg_color;\n"
+#define LIGHT_CSS_SUFFIX \
+  "@define-color popover_bg_color mix(@window_bg_color, white, .1);\n" \
+  "@define-color card_bg_color alpha(white, .6);\n"
+#define DARK_CSS_SUFFIX \
+  "@define-color popover_bg_color mix(@window_bg_color, white, 0.07);\n" \
+  "@define-color card_bg_color @popover_bg_color;\n" \
+  "@define-color view_bg_color darker(@window_bg_color);\n"
+
+enum {
+  FOREGROUND,
+  BACKGROUND,
+};
+
+static gboolean
+get_color (GtkSourceStyleScheme *scheme,
+           const char           *style_name,
+           GdkRGBA              *color,
+           int                   kind)
+{
+  GtkSourceStyle *style;
+  g_autofree char *fg = NULL;
+  g_autofree char *bg = NULL;
+  gboolean fg_set = FALSE;
+  gboolean bg_set = FALSE;
+
+  g_assert (GTK_SOURCE_IS_STYLE_SCHEME (scheme));
+  g_assert (style_name != NULL);
+
+  if (!(style = gtk_source_style_scheme_get_style (scheme, style_name)))
+    return FALSE;
+
+  g_object_get (style,
+                "foreground", &fg,
+                "foreground-set", &fg_set,
+                "background", &bg,
+                "background-set", &bg_set,
+                NULL);
+
+  if (kind == FOREGROUND && fg && fg_set)
+    gdk_rgba_parse (color, fg);
+  else if (kind == BACKGROUND && bg && bg_set)
+    gdk_rgba_parse (color, bg);
+  else
+    return FALSE;
+
+  return color->alpha >= .1;
+}
+
+static inline gboolean
+get_foreground (GtkSourceStyleScheme *scheme,
+                const char           *style_name,
+                GdkRGBA              *fg)
+{
+  return get_color (scheme, style_name, fg, FOREGROUND);
+}
+
+static inline gboolean
+get_background (GtkSourceStyleScheme *scheme,
+                const char           *style_name,
+                GdkRGBA              *bg)
+{
+  return get_color (scheme, style_name, bg, BACKGROUND);
+}
+
+static gboolean
+get_metadata_color (GtkSourceStyleScheme *scheme,
+                    const char           *key,
+                    GdkRGBA              *color)
+{
+  const char *str;
+
+  if ((str = gtk_source_style_scheme_get_metadata (scheme, key)))
+    return gdk_rgba_parse (color, str);
+
+  return FALSE;
+}
+
+static void
+define_color (GString       *str,
+              const char    *name,
+              const GdkRGBA *color)
+{
+  g_autofree char *color_str = NULL;
+  GdkRGBA opaque;
+
+  g_assert (str != NULL);
+  g_assert (name != NULL);
+  g_assert (color != NULL);
+
+  opaque = *color;
+  opaque.alpha = 1.0f;
+
+  color_str = gdk_rgba_to_string (&opaque);
+  g_string_append_printf (str, "@define-color %s %s;\n", name, color_str);
+}
+
+static void
+define_color_mixed (GString       *str,
+                    const char    *name,
+                    const GdkRGBA *a,
+                    const GdkRGBA *b,
+                    double         level)
+{
+  g_autofree char *a_str = NULL;
+  g_autofree char *b_str = NULL;
+  char levelstr[G_ASCII_DTOSTR_BUF_SIZE];
+
+  g_assert (str != NULL);
+  g_assert (name != NULL);
+  g_assert (a != NULL);
+  g_assert (b != NULL);
+
+  a_str = gdk_rgba_to_string (a);
+  b_str = gdk_rgba_to_string (b);
+
+  g_ascii_dtostr (levelstr, sizeof levelstr, level);
+
+  /* truncate */
+  levelstr[6] = 0;
+
+  g_string_append_printf (str, "@define-color %s mix(%s,%s,%s);\n", name, a_str, b_str, levelstr);
+}
+
+#if 0
+static inline void
+premix_colors (GdkRGBA       *dest,
+               const GdkRGBA *fg,
+               const GdkRGBA *bg,
+               gboolean       bg_set,
+               double         alpha)
+{
+  g_assert (dest != NULL);
+  g_assert (fg != NULL);
+  g_assert (bg != NULL || bg_set == FALSE);
+  g_assert (alpha >= 0.0 && alpha <= 1.0);
+
+  if (bg_set)
+    {
+      dest->red = ((1 - alpha) * bg->red) + (alpha * fg->red);
+      dest->green = ((1 - alpha) * bg->green) + (alpha * fg->green);
+      dest->blue = ((1 - alpha) * bg->blue) + (alpha * fg->blue);
+      dest->alpha = 1.0;
+    }
+  else
+    {
+      *dest = *fg;
+      dest->alpha = alpha;
+    }
+}
+#endif
+
+gboolean
+_ide_source_style_scheme_is_dark (GtkSourceStyleScheme *scheme)
+{
+  const char *id = gtk_source_style_scheme_get_id (scheme);
+  const char *variant = gtk_source_style_scheme_get_metadata (scheme, "variant");
+  GdkRGBA text_bg;
+
+  if (g_strcmp0 (variant, "light") == 0)
+    return FALSE;
+  else if (g_strcmp0 (variant, "dark") == 0)
+    return TRUE;
+  else if (strstr (id, "-dark") != NULL)
+    return TRUE;
+
+  if (get_background (scheme, "text", &text_bg))
+    {
+      /* http://alienryderflex.com/hsp.html */
+      double r = text_bg.red * 255.0;
+      double g = text_bg.green * 255.0;
+      double b = text_bg.blue * 255.0;
+      double hsp = sqrt (0.299 * (r * r) +
+                         0.587 * (g * g) +
+                         0.114 * (b * b));
+
+      return hsp <= 127.5;
+    }
+
+  return FALSE;
+}
+
+char *
+_ide_recoloring_generate_css (GtkSourceStyleScheme *style_scheme)
+{
+  static const GdkRGBA black = {0,0,0,1};
+  static const GdkRGBA white = {1,1,1,1};
+  const GdkRGBA *alt;
+  GdkRGBA text_bg;
+  GdkRGBA text_fg;
+  GdkRGBA right_margin;
+  const char *id;
+  const char *name;
+  GString *str;
+  GdkRGBA color;
+  gboolean is_dark;
+  gboolean has_fg;
+  gboolean has_bg;
+
+  g_return_val_if_fail (GTK_SOURCE_IS_STYLE_SCHEME (style_scheme), NULL);
+
+  /* Don't restyle Adwaita as we already have it */
+  id = gtk_source_style_scheme_get_name (style_scheme);
+  if (g_str_has_prefix (id, "Adwaita"))
+    return NULL;
+
+  name = gtk_source_style_scheme_get_name (style_scheme);
+  is_dark = _ide_source_style_scheme_is_dark (style_scheme);
+  alt = is_dark ? &white : &black;
+
+  str = g_string_new (SHARED_CSS);
+  g_string_append_printf (str, "/* %s */\n", name);
+
+  /* TODO: Improve error checking and fallbacks */
+
+  has_bg = get_background (style_scheme, "text", &text_bg);
+  has_fg = get_foreground (style_scheme, "text", &text_fg);
+  get_background (style_scheme, "right-margin", &right_margin);
+  right_margin.alpha = 1;
+
+  if (get_metadata_color (style_scheme, "window_bg_color", &color))
+    define_color (str, "window_bg_color", &color);
+  else if (has_bg && has_fg)
+    define_color (str, "window_bg_color", &text_bg);
+  else if (is_dark)
+    define_color_mixed (str, "window_bg_color", &text_bg, alt, .025);
+  else
+    define_color_mixed (str, "window_bg_color", &text_bg, &white, .1);
+
+  if (get_metadata_color (style_scheme, "window_fg_color", &color))
+    define_color (str, "window_fg_color", &color);
+  else if (has_bg && has_fg)
+    define_color (str, "window_fg_color", &text_fg);
+  else if (is_dark)
+    define_color_mixed (str, "window_fg_color", &text_bg, alt, .05);
+  else
+    define_color_mixed (str, "window_fg_color", &text_bg, alt, .025);
+
+  if (get_metadata_color (style_scheme, "headerbar_bg_color", &color))
+    define_color (str, "headerbar_bg_color", &color);
+  else if (has_bg && has_fg)
+    define_color_mixed (str, "headerbar_bg_color", &text_bg, &text_fg, .05);
+  else if (is_dark)
+    define_color_mixed (str, "headerbar_bg_color", &text_bg, alt, .025);
+  else
+    define_color_mixed (str, "headerbar_bg_color", &text_bg, &white, .1);
+
+  if (get_metadata_color (style_scheme, "headerbar_fg_color", &color))
+    define_color (str, "headerbar_fg_color", &color);
+  else if (has_bg && has_fg)
+    define_color (str, "headerbar_fg_color", &text_fg);
+  else if (is_dark)
+    define_color_mixed (str, "headerbar_fg_color", &text_bg, alt, .05);
+  else
+    define_color_mixed (str, "headerbar_fg_color", &text_bg, alt, .025);
+
+  define_color_mixed (str, "view_bg_color", &text_bg, &white, is_dark ? .1 : .3);
+  define_color (str, "view_fg_color", &text_fg);
+
+  if (get_metadata_color (style_scheme, "accent_bg_color", &color) ||
+      get_background (style_scheme, "selection", &color))
+    define_color (str, "accent_bg_color", &color);
+
+  if (get_metadata_color (style_scheme, "accent_fg_color", &color) ||
+      get_foreground (style_scheme, "selection", &color))
+    define_color (str, "accent_fg_color", &color);
+
+  if (get_metadata_color (style_scheme, "accent_color", &color))
+    {
+      define_color (str, "accent_color", &color);
+    }
+  else if (get_metadata_color (style_scheme, "accent_bg_color", &color) ||
+           get_background (style_scheme, "selection", &color))
+    {
+      color.alpha = 1;
+      define_color_mixed (str, "accent_color", &color, alt, .1);
+    }
+
+  if (is_dark)
+    g_string_append (str, DARK_CSS_SUFFIX);
+  else
+    g_string_append (str, LIGHT_CSS_SUFFIX);
+
+  return g_string_free (str, FALSE);
+}
+
+GtkSourceStyleScheme *
+_ide_source_style_scheme_get_variant (GtkSourceStyleScheme *scheme,
+                                      const char           *variant)
+{
+  GtkSourceStyleSchemeManager *style_scheme_manager;
+  GtkSourceStyleScheme *ret;
+  g_autoptr(GString) str = NULL;
+  g_autofree char *key = NULL;
+  const char *mapping;
+
+  g_return_val_if_fail (GTK_SOURCE_IS_STYLE_SCHEME (scheme), NULL);
+  g_return_val_if_fail (g_strcmp0 (variant, "light") == 0 ||
+                        g_strcmp0 (variant, "dark") == 0, NULL);
+
+  style_scheme_manager = gtk_source_style_scheme_manager_get_default ();
+
+  /* If the scheme provides "light-variant" or "dark-variant" metadata,
+   * we will prefer those if the variant is available.
+   */
+  key = g_strdup_printf ("%s-variant", variant);
+  if ((mapping = gtk_source_style_scheme_get_metadata (scheme, key)))
+    {
+      if ((ret = gtk_source_style_scheme_manager_get_scheme (style_scheme_manager, mapping)))
+        return ret;
+    }
+
+  /* Try to find a match by replacing -light/-dark with @variant */
+  str = g_string_new (gtk_source_style_scheme_get_id (scheme));
+
+  if (g_str_has_suffix (str->str, "-light"))
+    g_string_truncate (str, str->len - strlen ("-light"));
+  else if (g_str_has_suffix (str->str, "-dark"))
+    g_string_truncate (str, str->len - strlen ("-dark"));
+
+  g_string_append_printf (str, "-%s", variant);
+
+  /* Look for "Foo-variant" directly */
+  if ((ret = gtk_source_style_scheme_manager_get_scheme (style_scheme_manager, str->str)))
+    return ret;
+
+  /* Look for "Foo" */
+  g_string_truncate (str, str->len - strlen (variant) - 1);
+  if ((ret = gtk_source_style_scheme_manager_get_scheme (style_scheme_manager, str->str)))
+    return ret;
+
+  /* Fallback to what we were provided */
+  return ret;
+}
+
diff --git a/src/libide/gui/meson.build b/src/libide/gui/meson.build
index fb800f21f..d138c6a45 100644
--- a/src/libide/gui/meson.build
+++ b/src/libide/gui/meson.build
@@ -51,6 +51,7 @@ libide_gui_private_headers = [
   'ide-notification-view-private.h',
   'ide-preferences-builtin-private.h',
   'ide-primary-workspace-private.h',
+  'ide-recoloring-private.h',
   'ide-session-private.h',
 ]
 
@@ -64,6 +65,7 @@ libide_gui_private_sources = [
   'ide-notification-view.c',
   'ide-preferences-builtin.c',
   'ide-primary-workspace-actions.c',
+  'ide-recoloring.c',
   'ide-session.c',
   'ide-workspace-actions.c',
 ]
@@ -137,6 +139,8 @@ libide_gui_sources += [libide_gui_enums[0]]
 #
 
 libide_gui_deps = [
+  cc.find_library('m', required: false),
+
   libgio_dep,
   libgtk_dep,
   libgtksource_dep,