Add support for adjusting the font scale at runtime

5 files changed, 77 insertions, 4 deletions

diff --git a/Makefile b/Makefile
index 39463aa..1f61888 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ MANDIR ?= ${DATAROOTDIR}/man
 VALAC ?= valac
 
 weltschmerz: weltschmerz.vala terminal.vala config.vala resources.c
-	${VALAC} --pkg posix --pkg gtk+-3.0 --pkg vte-2.91 --gresources resources.xml \
+	${VALAC} -X -lm --pkg posix --pkg gtk+-3.0 --pkg vte-2.91 --gresources resources.xml \
 		weltschmerz.vala terminal.vala config.vala resources.c
 
 resources.c: resources.xml terminal.ui terminal.css
diff --git a/meson.build b/meson.build
index a36157b..0115018 100644
--- a/meson.build
+++ b/meson.build
@@ -2,9 +2,11 @@ project('weltschmerz', 'vala', 'c')
 
 gnome = import('gnome')
 valac = meson.get_compiler('vala')
+cc    = meson.get_compiler('c')
 
 dependencies = [
   valac.find_library('posix'),
+  cc.find_library('m', required: false),
   dependency('gtk+-3.0'),
   dependency('vte-2.91'),
 ]
diff --git a/terminal.ui b/terminal.ui
index 7885ecc..c82a04d 100644
--- a/terminal.ui
+++ b/terminal.ui
@@ -59,6 +59,7 @@
             <signal name="button-release-event" handler="vte_button_release" swapped="no"/>
             <signal name="child-exited" handler="gtk_main_quit" swapped="no"/>
             <signal name="key-press-event" handler="vte_key_press" swapped="no"/>
+            <signal name="scroll-event" handler="vte_scroll" swapped="no"/>
             <signal name="window-title-changed" handler="window_set_title" swapped="no"/>
           </object>
         </child>
diff --git a/terminal.vala b/terminal.vala
index d0f9480..c6c2525 100644
--- a/terminal.vala
+++ b/terminal.vala
@@ -9,6 +9,15 @@ class Terminal : Gtk.Overlay {
 	const uint PCRE2_JIT_PARTIAL_SOFT = 0x00000002u;
 	const uint PCRE2_ERROR_JIT_BADOPTION = -45;
 
+	/* The following values were chosen to be powers of 1.2 that lie within the
+	 * range of VTE's bounds for the font scale: [0.25, 4].
+	 *
+	 * They allow for 7 steps above or below the default scale of 1.
+	 */
+	const double FONT_SCALE_MIN = 0.2790816472336535; // 1.2 ^ -7
+	const double FONT_SCALE_MAX = 3.583180799999999;  // 1.2 ^ 7
+	const double FONT_SCALE_FACTOR = 1.2;
+
 	struct PaletteEntry {
 		string name;
 		string normal;
@@ -42,6 +51,7 @@ class Terminal : Gtk.Overlay {
 	bool has_search;
 	string url_match;
 	uint? infobar_timeout_id;
+	double scroll_delta;
 
 	public Terminal(string[] args, Gtk.Container parent, Gtk.Window window) {
 		Object(parent: parent, window: window);
@@ -135,12 +145,16 @@ class Terminal : Gtk.Overlay {
 		}
 	}
 
+	bool match_modifiers(int state, Gdk.ModifierType modifiers) {
+		return (state & modifiers) == modifiers;
+	}
+
 	bool match_button(Gdk.EventButton event, Gdk.ModifierType modifiers, uint button) {
-		return (event.state & modifiers) == modifiers && event.button == button;
+		return match_modifiers(event.state, modifiers) && event.button == button;
 	}
 
 	bool match_key(Gdk.EventKey event, Gdk.ModifierType modifiers, uint key) {
-		return (event.state & modifiers) == modifiers && event.keyval == key;
+		return match_modifiers(event.state, modifiers) && event.keyval == key;
 	}
 
 	void infobar_show(string message, Gtk.MessageType level, uint? timeout = null) {
@@ -300,6 +314,18 @@ class Terminal : Gtk.Overlay {
 		clipboard.set_text(url_match, -1);
 	}
 
+	void adjust_font_scale(double scale) {
+		vte.set_font_scale(scale.clamp(FONT_SCALE_MIN, FONT_SCALE_MAX));
+	}
+
+	void increase_font_scale() {
+		adjust_font_scale(vte.get_font_scale() * FONT_SCALE_FACTOR);
+	}
+
+	void decrease_font_scale() {
+		adjust_font_scale(vte.get_font_scale() / FONT_SCALE_FACTOR);
+	}
+
 	[GtkCallback]
 	void vte_copy() {
 		if (vte.get_has_selection()) {
@@ -366,6 +392,41 @@ class Terminal : Gtk.Overlay {
 			return true;
 		}
 
+		if (match_key(event, CONTROL_MASK, Gdk.Key.@0)) {
+			vte.set_font_scale(1.0);
+			return true;
+		}
+
+		if (match_key(event, CONTROL_MASK, Gdk.Key.equal)) {
+			increase_font_scale();
+			return true;
+		}
+
+		if (match_key(event, CONTROL_MASK, Gdk.Key.minus)) {
+			decrease_font_scale();
+			return true;
+		}
+
+		return false;
+	}
+
+	[GtkCallback]
+	bool vte_scroll(Gdk.EventScroll event) {
+		if (match_modifiers(event.state, CONTROL_MASK)) {
+			scroll_delta += event.delta_y;
+
+			if (Math.fabs(scroll_delta) >= 1) {
+				if (scroll_delta < 0) {
+					increase_font_scale();
+				} else {
+					decrease_font_scale();
+				}
+				scroll_delta = 0;
+			}
+
+			return true;
+		}
+
 		return false;
 	}
 
diff --git a/weltschmerz.1 b/weltschmerz.1
index 7c248c5..bb834b5 100644
--- a/weltschmerz.1
+++ b/weltschmerz.1
@@ -1,4 +1,4 @@
-.Dd January 17, 2019
+.Dd August 31, 2019
 .Dt WELTSCHMERZ 1
 .Os
 .Sh NAME
@@ -26,6 +26,15 @@ The clipboard can be copied to and pasted from with
 and
 .Sy CTRL + Shift + V ,
 respectively.
+.Pp
+The font scale can be adjusted by scrolling up or down whilst holding
+.Sy CTRL ,
+or by using
+.Sy CTRL + =
+and
+.Sy CTRL + - .
+It can be reset to its default value with
+.Sy CTRL + 0 .
 .Sh SEARCH OVERLAY
 The search overlay can be opened by pressing
 .Sy CTRL + Shift + F .