Gtk UI: full color scheme support

 * implemented by exporting the most important Scintilla STYLEs
   as CSS variables and defining named widgets for the main UI
   components.
 * ~/.teco_css will then apply the Scintilla styles to the
   Gtk UI.
   This file is also for additional tweaks, e.g. enabling
   translucency.
 * A fallback.css is provided which does just that and is able
   to apply the terminal.tes and solarized.tes color schemes.
 * Other important aspects of theming like font sizes and names
   have not yet been dealt with.
   (We may want to apply the corresponding Scintilla settings
   to some widgets...)

7 files changed, 234 insertions, 18 deletions

diff --git a/doc/sciteco.1.in b/doc/sciteco.1.in
index 1d21ecf..0a96cab 100644
--- a/doc/sciteco.1.in
+++ b/doc/sciteco.1.in
@@ -314,6 +314,19 @@ standard library \fBsession.tes\fP macros.
 When the \(lqsession.vcs\(rq macro is used, these files
 will also be created in the roots of Git, Mercurial and
 Subversion repositories or working copies.
+.TP
+.B $SCITECOCONFIG/.teco_css
+When using the Gtk UI, this will be the location of a
+CSS file that can be used to apply \*(ST color schemes
+to the entire UI and to do other style customizations.
+.TP
+.B @pkgdatadir@/fallback.css
+When using the Gtk UI, this is a fallback stylesheet
+in case
+.B $SCITECOCONFIG/.teco_css
+does not exist.
+It may also be used as a template for
+.BR $SCITECOCONFIG/.teco_css .
 .
 .
 .SH SEE ALSO
diff --git a/doc/sciteco.7.template b/doc/sciteco.7.template
index bdb25bc..9f3ba8f 100644
--- a/doc/sciteco.7.template
+++ b/doc/sciteco.7.template
@@ -688,6 +688,48 @@ macro or \fBED\fP hook (for syntax highlighting).
 \*(ST ships with a standard library with color schemes
 and lexer configurations for a wide range of languages.
 .
+.SS Gtk CSS Styling
+.
+While the tools mentioned above are sufficient for
+Curses UIs, the Gtk+ 3 UI has many more styling possibilities.
+The basic color scheme will be automatically effective for
+the buffer view since this is handled by Scintilla.
+In order to apply the color scheme to the other UI components,
+a CSS file must be provided that overrides certain styling
+settings of the Gtk theme.
+.LP
+Therefore \*(ST automatically exports the following Gtk
+CSS variables that can be referred to by user-provided
+CSS files:
+.TP
+.B @sciteco_default_fg_color
+The foreground color of Scintilla's \fBSTYLE_DEFAULT\fP.
+.TP
+.B @sciteco_default_bg_color
+The background color of Scintilla's \fBSTYLE_DEFAULT\fP.
+.TP
+.B @sciteco_calltip_fg_color
+The foreground color of Scintilla's \fBSTYLE_CALLTIP\fP.
+.TP
+.B @sciteco_calltip_bg_color
+The background color of Scintilla's \fBSTYLE_CALLTIP\fP.
+.LP
+Furthermore, \*(ST defines the following named widgets for its
+main UI components: \fB#sciteco-info-bar\fP, \fB#sciteco-message-bar\fP,
+\fB#sciteco-cmdline\fP and \fB#sciteco-info-popup\fP.
+.LP
+The CSS file is loaded from
+.B $SCITECOCONFIG/.teco_css
+if it is existing.
+Else, \*(ST loads the fallback CSS at
+.BR @pkgdatadir@/fallback.css ,
+which can also be used as a template when writing \fB.teco_css\fP.
+The CSS file can be written such that it works for any
+\*(ST color scheme and may also be used to tweak other
+aspects of \*(ST's user interface.
+Please refer to the Gtk documentation for more details on
+CSS theming.
+.
 .
 .SH ARITHMETICS AND EXPRESSIONS
 .
@@ -1792,6 +1834,12 @@ Scinterm manual, documenting the mapping of
 .UR http://foicica.com/scinterm/manual.html
 Scinterm manual
 .UE
+.TP
+Gtk+ 3 documentation, containg details about
+its CSS support and syntax:
+.UR https://developer.gnome.org/gtk3/stable/GtkCssProvider.html
+GtkCssProvider
+.UE
 .
 .
 .SH AUTHOR
diff --git a/src/interface-gtk/Makefile.am b/src/interface-gtk/Makefile.am
index 64b4625..51591e1 100644
--- a/src/interface-gtk/Makefile.am
+++ b/src/interface-gtk/Makefile.am
@@ -17,6 +17,8 @@ libsciteco_interface_la_SOURCES += gtkflowbox.c gtkflowbox.h
 endif
 nodist_libsciteco_interface_la_SOURCES = gtk-info-popup.c
 
+dist_pkgdata_DATA = fallback.css
+
 CLEANFILES = $(BUILT_SOURCES)
 
 %.c %.h %-private.h : %.gob
diff --git a/src/interface-gtk/fallback.css b/src/interface-gtk/fallback.css
new file mode 100644
index 0000000..0482763
--- /dev/null
+++ b/src/interface-gtk/fallback.css
@@ -0,0 +1,47 @@
+/*
+ * This CSS will loaded as a fallback if there is no
+ * $SCITECOCONFIG/.teco_css.
+ * It tries to apply the current SciTECO color scheme
+ * by using predefined variables (see sciteco(7)).
+ * This may cause problems with your current Gtk theme.
+ * You can copy this file to $SCITECOCONFIG/.teco_css
+ * to fix it up or add other style customizations.
+ */
+
+/*
+ * Original STYLE_DEFAULT foregrounds on backgrounds:
+ */
+#sciteco-cmdline {
+	color: @sciteco_default_fg_color;
+	text-shadow: none;
+	background-color: @sciteco_default_bg_color;
+	background-image: none;
+}
+
+/*
+ * Reversed STYLE_DEFAULT colors:
+ * The "question" class refers to G_MESSAGE_QUESTION.
+ * This is used for showing user-level messages for the sole
+ * reason that there is no class for G_MESSAGE_OTHER that
+ * we could use for styling.
+ */
+#sciteco-info-bar,
+#sciteco-info-bar GtkLabel,
+.titlebar, /* info bar in CSD mode */
+#sciteco-message-bar.question {
+	color: @sciteco_default_bg_color;
+	text-shadow: none;
+	background-color: @sciteco_default_fg_color;
+	background-image: none;
+}
+
+/*
+ * The popup widget (uses STYLE_CALLTIP)
+ */
+#sciteco-info-popup,
+#sciteco-info-popup GtkLabel {
+	color: @sciteco_calltip_fg_color;
+	text-shadow: none;
+	background-color: @sciteco_calltip_bg_color;
+	background-image: none;
+}
diff --git a/src/interface-gtk/gtk-info-popup.gob b/src/interface-gtk/gtk-info-popup.gob
index f172de6..6cb1b81 100644
--- a/src/interface-gtk/gtk-info-popup.gob
+++ b/src/interface-gtk/gtk-info-popup.gob
@@ -44,6 +44,10 @@ enum GTK_INFO_POPUP {
 	DIRECTORY
 } Gtk:Info:Popup:Entry:Type;
 
+/*
+ * NOTE: Deriving from GtkEventBox ensures that we can
+ * set a background on the entire popup widget.
+ */
 class Gtk:Info:Popup from Gtk:Event:Box {
 	public GtkAdjustment *hadjustment;
 	public GtkAdjustment *vadjustment;
@@ -92,18 +96,10 @@ class Gtk:Info:Popup from Gtk:Event:Box {
 		gtk_widget_show_all(box);
 
 		/*
-		 * The top-level widget is a GtkEventBox, so it can have
-		 * a background. We assign a default color since the popup
-		 * will usually be put in an overlay and we don't want it
-		 * to be transparent.
-		 * It can also be styled with rounded corners etc.
-		 * FIXME: This method of setting a background color is
-		 * deprecated. We are supposed to use CSS style providers...
+		 * NOTE: Everything shown except the top-level container.
+		 * Therefore a gtk_widget_show() is enough to show our popup.
 		 */
 		gtk_container_add(GTK_CONTAINER(self), box);
-		GdkRGBA color = {0.5, 0.5, 0.5, 1.0};
-		gtk_widget_override_background_color(GTK_WIDGET(self), GTK_STATE_FLAG_NORMAL,
-		                                     &color);
 	}
 
 	/**
diff --git a/src/interface-gtk/interface-gtk.cpp b/src/interface-gtk/interface-gtk.cpp
index ebd3c91..7938131 100644
--- a/src/interface-gtk/interface-gtk.cpp
+++ b/src/interface-gtk/interface-gtk.cpp
@@ -25,6 +25,7 @@
 
 #include <glib.h>
 #include <glib/gprintf.h>
+#include <glib/gstdio.h>
 
 /*
  * FIXME: Because of gdk_threads_enter().
@@ -42,11 +43,11 @@
 
 #include <gio/gio.h>
 
-#include "gtk-info-popup.h"
-
 #include <Scintilla.h>
 #include <ScintillaWidget.h>
 
+#include "gtk-info-popup.h"
+
 #include "sciteco.h"
 #include "string-utils.h"
 #include "cmdline.h"
@@ -84,7 +85,24 @@ static gboolean sigterm_handler(gpointer user_data) G_GNUC_UNUSED;
 
 } /* extern "C" */
 
-#define UNNAMED_FILE "(Unnamed)"
+#define UNNAMED_FILE		"(Unnamed)"
+
+#define USER_CSS_FILE		".teco_css"
+
+/** printf() format for CSS RGB colors given as guint32 */
+#define CSS_COLOR_FORMAT	"#%06" G_GINT32_MODIFIER "X"
+
+/**
+ * Convert Scintilla-style BGR color triple to
+ * RGB.
+ */
+static inline guint32
+bgr2rgb(guint32 bgr)
+{
+	return ((bgr & 0x0000FF) << 16) |
+	       ((bgr & 0x00FF00) << 0) |
+	       ((bgr & 0xFF0000) >> 16);
+}
 
 void
 ViewGtk::initialize_impl(void)
@@ -189,6 +207,7 @@ InterfaceGtk::main_impl(int &argc, char **&argv)
 	 * FIXME: At lease on Gtk 3.12 we could disable the subtitle.
 	 */
 	info_bar_widget = gtk_header_bar_new();
+	gtk_widget_set_name(info_bar_widget, "sciteco-info-bar");
 	info_image = gtk_image_new();
 	gtk_header_bar_pack_start(GTK_HEADER_BAR(info_bar_widget), info_image);
 	if (use_csd) {
@@ -214,6 +233,7 @@ InterfaceGtk::main_impl(int &argc, char **&argv)
 	gtk_box_pack_start(GTK_BOX(vbox), overlay_widget, TRUE, TRUE, 0);
 
 	message_bar_widget = gtk_info_bar_new();
+	gtk_widget_set_name(message_bar_widget, "sciteco-message-bar");
 	message_bar_content = gtk_info_bar_get_content_area(GTK_INFO_BAR(message_bar_widget));
 	message_widget = gtk_label_new("");
 	gtk_misc_set_alignment(GTK_MISC(message_widget), 0., 0.);
@@ -221,6 +241,7 @@ InterfaceGtk::main_impl(int &argc, char **&argv)
 	gtk_box_pack_start(GTK_BOX(vbox), message_bar_widget, FALSE, FALSE, 0);
 
 	cmdline_widget = gtk_entry_new();
+	gtk_widget_set_name(cmdline_widget, "sciteco-cmdline");
 	gtk_entry_set_has_frame(GTK_ENTRY(cmdline_widget), FALSE);
 	gtk_editable_set_editable(GTK_EDITABLE(cmdline_widget), FALSE);
 	widget_set_font(cmdline_widget, "Courier");
@@ -236,6 +257,7 @@ InterfaceGtk::main_impl(int &argc, char **&argv)
 	 * filling the entire width.
 	 */
 	popup_widget = gtk_info_popup_new();
+	gtk_widget_set_name(popup_widget, "sciteco-info-popup");
 	gtk_overlay_add_overlay(GTK_OVERLAY(overlay_widget), popup_widget);
 	g_signal_connect(overlay_widget, "get-child-position",
 	                 G_CALLBACK(gtk_info_popup_get_position_in_overlay), NULL);
@@ -248,8 +270,13 @@ InterfaceGtk::main_impl(int &argc, char **&argv)
 void
 InterfaceGtk::vmsg_impl(MessageType type, const gchar *fmt, va_list ap)
 {
+	/*
+	 * The message types are chosen such that there is a CSS class
+	 * for every one of them. GTK_MESSAGE_OTHER does not have
+	 * a CSS class.
+	 */
 	static const GtkMessageType type2gtk[] = {
-		/* [MSG_USER]		= */ GTK_MESSAGE_OTHER,
+		/* [MSG_USER]		= */ GTK_MESSAGE_QUESTION,
 		/* [MSG_INFO]		= */ GTK_MESSAGE_INFO,
 		/* [MSG_WARNING]	= */ GTK_MESSAGE_WARNING,
 		/* [MSG_ERROR]		= */ GTK_MESSAGE_ERROR
@@ -285,7 +312,7 @@ InterfaceGtk::msg_clear(void)
 	gdk_threads_enter();
 
 	gtk_info_bar_set_message_type(GTK_INFO_BAR(message_bar_widget),
-				      GTK_MESSAGE_OTHER);
+				      GTK_MESSAGE_QUESTION);
 	gtk_label_set_text(GTK_LABEL(message_widget), "");
 
 	gdk_threads_leave();
@@ -482,6 +509,38 @@ InterfaceGtk::widget_set_font(GtkWidget *widget, const gchar *font_name)
 }
 
 void
+InterfaceGtk::set_css_variables_from_view(ViewGtk *view)
+{
+	gchar buffer[256];
+
+	/*
+	 * Generates a CSS that sets some predefined color variables.
+	 * This effectively "exports" Scintilla styles into the CSS
+	 * world.
+	 * Those colors are used by the fallback.css shipping with SciTECO
+	 * in order to apply the SciTECO-controlled color scheme to all the
+	 * predefined UI elements.
+	 * They can also be used in user-customizations.
+	 */
+	g_snprintf(buffer, sizeof(buffer),
+	           "@define-color sciteco_default_fg_color " CSS_COLOR_FORMAT ";"
+	           "@define-color sciteco_default_bg_color " CSS_COLOR_FORMAT ";"
+	           "@define-color sciteco_calltip_fg_color " CSS_COLOR_FORMAT ";"
+	           "@define-color sciteco_calltip_bg_color " CSS_COLOR_FORMAT ";",
+	           bgr2rgb(view->ssm(SCI_STYLEGETFORE, STYLE_DEFAULT)),
+	           bgr2rgb(view->ssm(SCI_STYLEGETBACK, STYLE_DEFAULT)),
+	           bgr2rgb(view->ssm(SCI_STYLEGETFORE, STYLE_CALLTIP)),
+	           bgr2rgb(view->ssm(SCI_STYLEGETBACK, STYLE_CALLTIP)));
+
+	/*
+	 * The GError and return value has been deprecated.
+	 * A CSS parsing error would point to a programming
+	 * error anyway.
+	 */
+	gtk_css_provider_load_from_data(css_var_provider, buffer, -1, NULL);
+}
+
+void
 InterfaceGtk::event_loop_impl(void)
 {
 	static const gchar *icon_files[] = {
@@ -491,6 +550,10 @@ InterfaceGtk::event_loop_impl(void)
 		NULL
 	};
 
+	GdkScreen *default_screen = gdk_screen_get_default();
+	GtkCssProvider *user_css_provider;
+	gchar *config_path, *user_css_file;
+
 	GList *icon_list = NULL;
 	GThread *thread;
 
@@ -516,6 +579,41 @@ InterfaceGtk::event_loop_impl(void)
 	refresh_info();
 
 	/*
+	 * Initialize the CSS variable provider and the CSS provider
+	 * for the included fallback.css.
+	 * NOTE: The return value of gtk_css_provider_load() is deprecated.
+	 * Instead we could register for the "parsing-error" signal.
+	 * For the time being we just silently ignore parsing errors.
+	 * They will be printed to stderr by Gtk anyway.
+	 */
+	css_var_provider = gtk_css_provider_new();
+	if (current_view)
+		/* set CSS variables initially */
+		set_css_variables_from_view(current_view);
+	gtk_style_context_add_provider_for_screen(default_screen,
+	                                          GTK_STYLE_PROVIDER(css_var_provider),
+	                                          GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
+	user_css_provider = gtk_css_provider_new();
+	/* get path of $SCITECOCONFIG/.teco_css */
+	config_path = QRegisters::globals["$SCITECOCONFIG"]->get_string();
+	user_css_file = g_build_filename(config_path, USER_CSS_FILE, NIL);
+	if (g_file_test(user_css_file, G_FILE_TEST_IS_REGULAR))
+		/* open user CSS */
+		gtk_css_provider_load_from_path(user_css_provider,
+		                                user_css_file, NULL);
+	else
+		/* use fallback CSS */
+		gtk_css_provider_load_from_path(user_css_provider,
+		                                SCITECODATADIR G_DIR_SEPARATOR_S
+		                                "fallback.css",
+		                                NULL);
+	g_free(user_css_file);
+	g_free(config_path);
+	gtk_style_context_add_provider_for_screen(default_screen,
+	                                          GTK_STYLE_PROVIDER(user_css_provider),
+	                                          GTK_STYLE_PROVIDER_PRIORITY_USER);
+
+	/*
 	 * When changing views, the new widget is not
 	 * added immediately to avoid flickering in the GUI.
 	 * It is only updated once per key press and only
@@ -702,6 +800,12 @@ InterfaceGtk::handle_key_press(bool is_shift, bool is_ctl, guint keyval)
 	}
 
 	/*
+	 * The styles configured via Scintilla might change
+	 * with every keypress.
+	 */
+	set_css_variables_from_view(current_view);
+
+	/*
 	 * The info area is updated very often and setting the
 	 * window title each time it is updated is VERY costly.
 	 * So we set it here once after every keypress even if the
@@ -739,8 +843,7 @@ InterfaceGtk::handle_key_press(bool is_shift, bool is_ctl, guint keyval)
 InterfaceGtk::~InterfaceGtk()
 {
 	g_free(info_current);
-	if (popup_widget)
-		gtk_widget_destroy(popup_widget);
+
 	if (window)
 		gtk_widget_destroy(window);
 
@@ -754,6 +857,9 @@ InterfaceGtk::~InterfaceGtk()
 
 		g_async_queue_unref(event_queue);
 	}
+
+	if (css_var_provider)
+		g_object_unref(css_var_provider);
 }
 
 /*
diff --git a/src/interface-gtk/interface-gtk.h b/src/interface-gtk/interface-gtk.h
index 4563d5f..eff4597 100644
--- a/src/interface-gtk/interface-gtk.h
+++ b/src/interface-gtk/interface-gtk.h
@@ -75,6 +75,8 @@ public:
 } ViewCurrent;
 
 typedef class InterfaceGtk : public Interface<InterfaceGtk, ViewGtk> {
+	GtkCssProvider *css_var_provider;
+
 	GtkWidget *window;
 	GtkWidget *vbox;
 
@@ -102,7 +104,7 @@ typedef class InterfaceGtk : public Interface<InterfaceGtk, ViewGtk> {
 	GAsyncQueue *event_queue;
 
 public:
-	InterfaceGtk() : Interface(),
+	InterfaceGtk() : css_var_provider(NULL),
 	                 window(NULL),
 	                 vbox(NULL),
 	                 info_type(INFO_TYPE_BUFFER), info_current(NULL),
@@ -170,6 +172,8 @@ public:
 private:
 	static void widget_set_font(GtkWidget *widget, const gchar *font_name);
 
+	void set_css_variables_from_view(ViewGtk *view);
+
 	void refresh_info(void);
 	void cmdline_insert_chr(gint &pos, gchar chr);
 } InterfaceCurrent;