Touchscreen: Improved scroll threshold

Remove the hardcoded (and way too small) scroll threshold (the distance moved in pixels before we think the users wants to scroll) and replace it with something based on the actual DPI of the screen.
On Android we call the API for that, on other touchscreens we reimplemented Android's formula (as of 2.2) and calculate it.

Flyspray: 11727

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28548 a1c6a512-1295-4272-9138-f99709370657

2 files changed, 32 insertions, 0 deletions

diff --git a/firmware/target/hosted/android/lcd-android.c b/firmware/target/hosted/android/lcd-android.c
index 78b1f12f7f..f4ef7b5e75 100644
--- a/firmware/target/hosted/android/lcd-android.c
+++ b/firmware/target/hosted/android/lcd-android.c
@@ -35,6 +35,8 @@ static jmethodID java_lcd_update;
 static jmethodID java_lcd_update_rect;
 
 static bool display_on;
+static int dpi;
+static int scroll_threshold;
 
 void lcd_init_device(void)
 {
@@ -77,6 +79,20 @@ void lcd_init_device(void)
                                                    RockboxFramebuffer_class,
                                                    "java_lcd_update_rect",
                                                    "(IIII)V");
+
+    jmethodID get_dpi    = e->GetMethodID(env_ptr,
+                                          RockboxFramebuffer_class,
+                                          "getDpi", "()I");
+
+    jmethodID get_scroll_threshold
+                         = e->GetMethodID(env_ptr,
+                                          RockboxFramebuffer_class,
+                                          "getScrollThreshold", "()I");
+
+    dpi              = e->CallIntMethod(env_ptr, RockboxFramebuffer_instance,
+                                        get_dpi);
+    scroll_threshold = e->CallIntMethod(env_ptr, RockboxFramebuffer_instance,
+                                        get_scroll_threshold);
     display_on = true;
 }
 
@@ -101,6 +117,16 @@ bool lcd_active(void)
     return display_on;
 }
 
+int lcd_get_dpi(void)
+{
+    return dpi;
+}
+
+int touchscreen_get_scroll_threshold(void)
+{
+    return scroll_threshold;
+}
+
 /*
  * (un)block lcd updates.
  *
diff --git a/firmware/target/hosted/sdl/lcd-sdl.c b/firmware/target/hosted/sdl/lcd-sdl.c
index 15e4ba95c3..96b1a04aa6 100644
--- a/firmware/target/hosted/sdl/lcd-sdl.c
+++ b/firmware/target/hosted/sdl/lcd-sdl.c
@@ -111,3 +111,9 @@ void sdl_set_gradient(SDL_Surface *surface, SDL_Color *start, SDL_Color *end,
     SDL_SetPalette(surface, SDL_LOGPAL|SDL_PHYSPAL, palette, first, steps);
 }
 
+int lcd_get_dpi(void)
+{
+    /* TODO: find a way to query it from the OS, SDL doesn't support it
+     * directly; for now assume the more or less standard 96 */
+    return 96;
+}