Revamp gui component

`gui` was tighly coupled to game logic, and could not be extended for
other purposes. Therefore, a generic GUI implementation, loosely
inspired by well-known GUI frameworks such as GTK, is now provided, with
the following properties:

- Does not depend on dynamic or static memory allocation, only automatic
(i.e., stack) memory allocation required.
- Portable among existing implementations.
- Simple to extend.
- Tiny memory footprint.

`gui` is now composed by GUI elements that can be chained to form a tree
structure. This is useful e.g.: to calculate X/Y coordinates for a given
GUI element given its parent(s).

This commit also refactors the older implementation, moving
game-specific logic into `player` and making use of the new component.

1 files changed, 14 insertions, 17 deletions

diff --git a/src/gui/inc/gui.h b/src/gui/inc/gui.h
index 254fd47..ec87f45 100644
--- a/src/gui/inc/gui.h
+++ b/src/gui/inc/gui.h
@@ -1,33 +1,30 @@
 #ifndef GUI_H
 #define GUI_H
 
+#include <camera.h>
 #include <gfx.h>
-#include <human_player.h>
+#include <peripheral.h>
 
 #ifdef __cplusplus
 extern "C"
 {
 #endif
 
-enum
+struct gui_common
 {
-    GUI_BAR_LEFT,
-    GUI_BAR_MID,
-    GUI_BAR_RIGHT,
-    GUI_SELECTION_UP_LEFT,
-    GUI_SELECTION_UP_RIGHT,
-    GUI_SELECTION_MID_VERT,
-    GUI_SELECTION_DOWN_LEFT,
-    GUI_SELECTION_DOWN_RIGHT,
-    GUI_SELECTION_MID,
-
-    MAX_GUI_SPRITES
+    int (*update)(struct gui_common *, const union peripheral *,
+        const struct camera *);
+    int (*render)(const struct gui_common *);
+    short x, y;
+    bool centered;
+    struct gui_common *parent, *child, *sibling;
 };
 
-void gui_update(struct human_player *h);
-int gui_render(const struct human_player *h);
-
-extern struct sprite gui_sprites[MAX_GUI_SPRITES];
+void gui_add_child(struct gui_common *parent, struct gui_common *child);
+void gui_add_sibling(struct gui_common *g, struct gui_common *sibling);
+int gui_update(struct gui_common *g, const union peripheral *p,
+    const struct camera *c);
+int gui_render(const struct gui_common *g);
 
 #ifdef __cplusplus
 }