Add some documenation

- proper mouse movement when display is rotated
- add simple way to get current monotonic clock time

Author: ardera

include/collection.h

@@ -5,6 +5,7 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <stdbool.h>
+#include <stdint.h>
 
 #include <pthread.h>
 
@@ -407,9 +408,14 @@ static inline void *memdup(const void *restrict src, const size_t n) {
 #define min(a, b) ((a) < (b) ? (a) : (b))
 #define max(a, b) ((a) > (b) ? (a) : (b))
 
+/**
+ * @brief Get the current time of the system monotonic clock.
+ * @returns time in nanoseconds.
+ */
 static inline uint64_t get_monotonic_time(void) {
-	/// TODO: Implement
-	return 0;
+	struct timespec time;
+	clock_gettime(CLOCK_MONOTONIC, &time);
+	return time.tv_nsec + time.tv_sec*1000000000ull;
 }
 
 #endif

include/flutter-pi.h

@@ -213,11 +213,17 @@ struct libudev {
 	 .skewY  = 0,                                 .scaleY = 1, .transY = 0, \
 	 .pers0  = -sin(((double) (deg))/180.0*M_PI), .pers1  = 0, .pers2  = cos(((double) (deg))/180.0*M_PI)})
 
+/**
+ * A flutter transformation that rotates any coords around the z-axis, counter-clockwise.
+ */
 #define FLUTTER_ROTZ_TRANSFORMATION(deg) ((FlutterTransformation) \
 	{.scaleX = cos(((double) (deg))/180.0*M_PI), .skewX  = -sin(((double) (deg))/180.0*M_PI), .transX = 0, \
 	 .skewY  = sin(((double) (deg))/180.0*M_PI), .scaleY = cos(((double) (deg))/180.0*M_PI),  .transY = 0, \
 	 .pers0  = 0,                                .pers1  = 0,                                 .pers2  = 1})
 
+/**
+ * A transformation that is the result of multiplying a with b.
+ */
 #define FLUTTER_MULTIPLIED_TRANSFORMATIONS(a, b) ((FlutterTransformation) \
 	{.scaleX = a.scaleX * b.scaleX + a.skewX  * b.skewY  + a.transX * b.pers0, \
 	 .skewX  = a.scaleX * b.skewX  + a.skewX  * b.scaleY + a.transX * b.pers1, \
@@ -229,12 +235,24 @@ struct libudev {
 	 .pers1  = a.pers0  * b.skewX  + a.pers1  * b.scaleY + a.pers2  * b.pers1, \
 	 .pers2  = a.pers0  * b.transX + a.pers1  * b.transY + a.pers2  * b.pers2})
 
+/**
+ * A transformation that is the result of adding a with b.
+ */
 #define FLUTTER_ADDED_TRANSFORMATIONS(a, b) ((FlutterTransformation) \
 	{.scaleX = a.scaleX + b.scaleX, .skewX  = a.skewX  + b.skewX,  .transX = a.transX + b.transX, \
 	 .skewY  = a.skewY  + b.skewY,  .scaleY = a.scaleY + b.scaleY, .transY = a.transY + b.transY, \
 	 .pers0  = a.pers0  + b.pers0,  .pers1  = a.pers1  + b.pers1,  .pers2  = a.pers2  + b.pers2 \
 	})
 
+/**
+ * A transformation that is the result of transponating a.
+ */
+#define FLUTTER_TRANSPONATED_TRANSFORMATION(a) ((FlutterTransformation) \
+	{.scaleX = a.scaleX, .skewX  = a.skewY,  .transX = a.pers0, \
+	 .skewY  = a.skewX,  .scaleY = a.scaleY, .transY = a.pers1, \
+	 .pers0  = a.transX, .pers1  = a.transY, .pers2  = a.pers2, \
+	})
+
 static inline void apply_flutter_transformation(
 	const FlutterTransformation t,
 	double *px,

include/user_input.h

@@ -98,6 +98,7 @@ struct user_input *user_input_new(
     const struct user_input_interface *interface, 
     void *userdata,
     const FlutterTransformation *display_to_view_transform,
+    const FlutterTransformation *view_to_display_transform,
 	unsigned int display_width,
 	unsigned int display_height
 );
@@ -116,10 +117,11 @@ void user_input_destroy(struct user_input *input);
  * @param display_to_view_transform will be copied internally.
  */
 void user_input_set_transform(
-	struct user_input *input,
-	const FlutterTransformation *display_to_view_transform,
-	unsigned int display_width,
-	unsigned int display_height 
+    struct user_input *input,
+    const FlutterTransformation *display_to_view_transform,
+    const FlutterTransformation *view_to_display_transform,
+    unsigned int display_width,
+    unsigned int display_height
 );
 
 /**

src/flutter-pi.c

@@ -1180,10 +1180,11 @@ int flutterpi_fill_view_properties(
 	}
 
 	if (flutterpi.user_input != NULL) {
-		// update the user input with the new transform
+		// update the user input with the new transforms
 		user_input_set_transform(
 			flutterpi.user_input,
 			&flutterpi.view.display_to_view_transform,
+			&flutterpi.view.view_to_display_transform,
 			flutterpi.display.width,
 			flutterpi.display.height
 		);
@@ -2585,6 +2586,7 @@ static int init_user_input(void) {
 		&user_input_interface,
 		&flutterpi,
 		&flutterpi.view.display_to_view_transform,
+		&flutterpi.view.view_to_display_transform,
 		flutterpi.display.width,
 		flutterpi.display.height
 	);

src/user_input.c

@@ -47,7 +47,7 @@ struct user_input {
      * used in the flutter pointer events
      */
     FlutterTransformation display_to_view_transform;
-    FlutterTransformation display_to_view_transform_nontranslating;
+    FlutterTransformation view_to_display_transform_nontranslating;
 	unsigned int display_width;
 	unsigned int display_height;
 
@@ -96,6 +96,7 @@ struct user_input *user_input_new(
     const struct user_input_interface *interface, 
     void *userdata,
     const FlutterTransformation *display_to_view_transform,
+    const FlutterTransformation *view_to_display_transform,
 	unsigned int display_width,
 	unsigned int display_height
 ) {
@@ -143,16 +144,19 @@ struct user_input *user_input_new(
 #endif
 
 	input->interface = *interface;
+    input->userdata = userdata;
+
 	input->libinput = libinput;
 	input->kbdcfg = kbdcfg;
 	input->next_unused_flutter_device_id = 0;
-
-    input->display_to_view_transform = *display_to_view_transform;
-    input->display_to_view_transform_nontranslating = *display_to_view_transform;
-    input->display_to_view_transform_nontranslating.transX = 0.0;
-    input->display_to_view_transform_nontranslating.transY = 0.0;
-    input->display_width = display_width;
-	input->display_height = display_height;
+    
+    user_input_set_transform(
+        input,
+        display_to_view_transform,
+        view_to_display_transform,
+        display_width,
+        display_height
+    );
 
     input->n_cursor_devices = 0;
     input->cursor_flutter_device_id = -1;
@@ -184,14 +188,18 @@ void user_input_destroy(struct user_input *input) {
 }
 
 void user_input_set_transform(
-	struct user_input *input,
-	const FlutterTransformation *display_to_view_transform,
-	unsigned int display_width,
-	unsigned int display_height 
+    struct user_input *input,
+    const FlutterTransformation *display_to_view_transform,
+    const FlutterTransformation *view_to_display_transform,
+    unsigned int display_width,
+    unsigned int display_height
 ) {
-	input->display_to_view_transform = *display_to_view_transform;
-	input->display_width = display_width;
-	input->display_height = display_height;
+    input->display_to_view_transform = *display_to_view_transform;
+    input->view_to_display_transform_nontranslating = *view_to_display_transform;
+    input->view_to_display_transform_nontranslating.transX = 0.0;
+    input->view_to_display_transform_nontranslating.transY = 0.0;
+    input->display_width = display_width;
+    input->display_height = display_height;
 }
 
 int user_input_get_fd(struct user_input *input) {
@@ -235,6 +243,9 @@ static void emit_pointer_events(struct user_input *input, const FlutterPointerEv
 
         // advance events so it points to the first remaining unemitted event
         events += to_copy;
+        
+        // advance the number of stored pointer events
+        input->n_collected_flutter_pointer_events += to_copy;
     }
 }
 
@@ -329,6 +340,8 @@ static int on_device_added(struct user_input *input, struct libinput_event *even
         libinput_device_set_user_data(device, NULL);
         free(data);
     }
+    
+    return 0;
 }
 
 static int on_device_removed(struct user_input *input, struct libinput_event *event, uint64_t timestamp) {
@@ -367,6 +380,8 @@ static int on_device_removed(struct user_input *input, struct libinput_event *ev
     }
 
     libinput_device_set_user_data(device, NULL);
+
+    return 0;
 }
 
 static int on_key_event(struct user_input *input, struct libinput_event *event) {
@@ -426,10 +441,12 @@ static int on_key_event(struct user_input *input, struct libinput_event *event)
         if (codepoint < 0x80) {
             // we emit UTF8 unconditionally here,
             // maybe we should check if codepoint is a control character?
-            input->interface.on_utf8_character(
-                input->userdata,
-                (uint8_t[1]) {codepoint}
-            );
+            if (isprint(codepoint)) {
+                input->interface.on_utf8_character(
+                    input->userdata,
+                    (uint8_t[1]) {codepoint}
+                );
+            }
         } else if (codepoint < 0x800) {
             input->interface.on_utf8_character(
                 input->userdata,
@@ -494,7 +511,7 @@ static int on_mouse_motion_event(struct user_input *input, struct libinput_event
     // we want the mouse to move in different directions as well.
     // the dx and dy is still in display (not view) coordinates though,
     // we only changed the movement direction.
-    apply_flutter_transformation(input->display_to_view_transform_nontranslating, &dx, &dy);
+    apply_flutter_transformation(input->view_to_display_transform_nontranslating, &dx, &dy);
 
     new_cursor_x = input->cursor_x + dx;
     new_cursor_y = input->cursor_y + dy;
@@ -590,6 +607,8 @@ static int on_mouse_motion_absolute_event(struct user_input *input, struct libin
         ),
         1
     );
+
+    return 0;
 }
 
 static int on_mouse_button_event(struct user_input *input, struct libinput_event *event) {