gg: handle Android's own native dpi scaling factor (#8908)

examples/2048/2048.v

@@ -255,7 +255,7 @@ fn (b Board) hmirror() Board {
 // GCC optimization bug; inlining fails when compiled with -prod
 [no_inline]
 fn (t TileLine) to_left() TileLine {
-	right_border_idx := 5
+	right_border_idx := 4
 	mut res := t
 	mut zeros := 0
 	mut nonzeros := 0
@@ -729,11 +729,11 @@ fn (mut app App) handle_tap() {
 	avgx, avgy := avg(s.pos.x, e.pos.x), avg(s.pos.y, e.pos.y)
 	// TODO: Replace "touch spots" with actual buttons
 	// bottom left -> change theme
-	if avgx < 200 && h - avgy < 200 {
+	if avgx < 50 && h - avgy < 50 {
 		app.next_theme()
 	}
 	// bottom right -> change tile format
-	if w - avgx < 200 && h - avgy < 200 {
+	if w - avgx < 50 && h - avgy < 50 {
 		app.next_tile_format()
 	}
 	if app.state == .victory {
@@ -767,7 +767,7 @@ fn (mut app App) handle_swipe() {
 	dmax := if max(adx, ady) > 0 { max(adx, ady) } else { 1 }
 	tdiff := int(e.time.unix_time_milli() - s.time.unix_time_milli())
 	// TODO: make this calculation more accurate (don't use arbitrary numbers)
-	min_swipe_distance := int(math.sqrt(min(w, h) * tdiff / 60)) + 20
+	min_swipe_distance := int(math.sqrt(min(w, h) * tdiff / 100)) + 20
 	if dmax < min_swipe_distance {
 		return
 	}

vlib/gg/gg.v

@@ -148,12 +148,7 @@ fn gg_init_sokol_window(user_data voidptr) {
 	gfx.setup(&desc)
 	sgl_desc := C.sgl_desc_t{}
 	sgl.setup(&sgl_desc)
-	g.scale = sapp.dpi_scale()
-	// NB: on older X11, `Xft.dpi` from ~/.Xresources, that sokol uses,
-	// may not be set which leads to sapp.dpi_scale reporting incorrectly 0.0
-	if g.scale < 0.1 {
-		g.scale = 1.0
-	}
+	g.scale = dpi_scale()
 	// is_high_dpi := sapp.high_dpi()
 	// fb_w := sapp.width()
 	// fb_h := sapp.height()
@@ -166,7 +161,7 @@ fn gg_init_sokol_window(user_data voidptr) {
 		g.ft = new_ft(
 			font_path: g.config.font_path
 			custom_bold_font_path: g.config.custom_bold_font_path
-			scale: sapp.dpi_scale()
+			scale: dpi_scale()
 		) or { panic(err) }
 		// println('FT took ${time.ticks()-t} ms')
 		g.font_inited = true
@@ -761,15 +756,21 @@ pub fn screen_size() Size {
 
 // window_size returns the `Size` of the active window
 pub fn window_size() Size {
-	mut s := sapp.dpi_scale()
-	if s == 0 {
-		s = 1.
-	}
+	s := dpi_scale()
 	return Size{int(sapp.width() / s), int(sapp.height() / s)}
 }
 
 pub fn dpi_scale() f32 {
-	return sapp.dpi_scale()
+	mut s := sapp.dpi_scale()
+	$if android {
+		s *= android_dpi_scale()
+	}
+	// NB: on older X11, `Xft.dpi` from ~/.Xresources, that sokol uses,
+	// may not be set which leads to sapp.dpi_scale reporting incorrectly 0.0
+	if s < 0.1 {
+		s = 1.
+	}
+	return s
 }
 
 pub fn high_dpi() bool {

vlib/gg/gg_android.c.v

@@ -0,0 +1,25 @@
+module gg
+
+import sokol.sapp
+
+#include <android/configuration.h>
+#include <android/native_activity.h>
+
+fn C.AConfiguration_new() voidptr
+fn C.AConfiguration_fromAssetManager(voidptr, voidptr)
+fn C.AConfiguration_getDensity(voidptr) u32
+fn C.AConfiguration_delete(voidptr)
+
+struct C.AAssetManager {}
+struct C.ANativeActivity {
+	assetManager voidptr
+}
+
+pub fn android_dpi_scale() f32 {
+	config := C.AConfiguration_new()
+	activity := &C.ANativeActivity(sapp.android_get_native_activity())
+	C.AConfiguration_fromAssetManager(config, activity.assetManager)
+	density := C.AConfiguration_getDensity(config)
+	C.AConfiguration_delete(config)
+	return f32(density) / 160
+}