Add experimental support for filters

Filters are a bit similar to tools, with a few difference:

- they only have a UI callback, but no ability to draw (for now at
  least).

- They don't require any icon or fixed action id, so we can more easily
  add filters: just need to add a c file with the FILTER_REGISTER macro.

- They show up in a special menu, instead of in the tool panel.

The idea is to use the filters for operations that don't require a full
drawing tool, like color correction, voxel effects, etc.

Still a work in progress.

src/filters.c

@@ -0,0 +1,54 @@
+/* Goxel 3D voxels editor
+ *
+ * copyright (c) 2024 Guillaume Chereau <guillaume@noctua-software.com>
+ *
+ * Goxel is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+
+ * Goxel is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+
+ * You should have received a copy of the GNU General Public License along
+ * with goxel.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "goxel.h"
+#include "../ext_src/stb/stb_ds.h"
+
+// stb array of registered filters.
+static filter_t **g_filters = NULL;
+
+static void a_filter_open(void *data)
+{
+    filter_t *filter = data;
+    LOG_D("Open filter %s", filter->name);
+    goxel.gui.current_filter = (filter_t*)data;
+}
+
+void filter_register_(filter_t *filter)
+{
+    action_t action;
+    action = (action_t) {
+        .id = filter->action_id,
+        .default_shortcut = filter->default_shortcut,
+        .cfunc_data = a_filter_open,
+        .data = (void*)filter,
+        .flags = ACTION_CAN_EDIT_SHORTCUT,
+    };
+    action_register(&action, 0);
+    arrput(g_filters, filter);
+}
+
+
+void filters_iter_all(
+        void *arg, void (*f)(void *arg, const filter_t *filter))
+{
+    int i;
+    for (i = 0; i < arrlen(g_filters); i++) {
+        f(arg, g_filters[i]);
+    }
+}

src/filters.h

@@ -0,0 +1,50 @@
+/* Goxel 3D voxels editor
+ *
+ * copyright (c) 2024 Guillaume Chereau <guillaume@noctua-software.com>
+ *
+ * Goxel is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+
+ * Goxel is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+
+ * You should have received a copy of the GNU General Public License along with
+ * goxel.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef FILTERS_H
+#define FILTERS_H
+
+typedef struct filter filter_t;
+
+struct filter {
+    int (*gui_fn)(filter_t *filter);
+    const char *name;
+    const char *action_id;
+    const char *default_shortcut;
+};
+
+#define FILTER_REGISTER(id_, klass_, ...) \
+    static klass_ GOX_filter_##id_ = {\
+            .filter = { \
+                .action_id = "filter_open_" #id_, __VA_ARGS__ \
+            } \
+        }; \
+    __attribute__((constructor)) \
+    static void GOX_register_filter_##id_(void) { \
+        filter_register_(&GOX_filter_##id_.filter); \
+    }
+
+void filter_register_(filter_t *filter);
+
+/**
+ * Iter all the registered filters
+ */
+void filters_iter_all(
+        void *arg, void (*f)(void *arg, const filter_t *filter));
+
+#endif // FILTERS_H

src/filters/dummy.c

@@ -0,0 +1,41 @@
+/* Goxel 3D voxels editor
+ *
+ * copyright (c) 2024-present Guillaume Chereau <guillaume@noctua-software.com>
+ *
+ * Goxel is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+
+ * Goxel is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+
+ * You should have received a copy of the GNU General Public License along with
+ * goxel.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "goxel.h"
+
+/*
+ * Dummy filter, just here for now until we have real filters.
+ */
+
+typedef struct {
+    filter_t filter;
+    int x;
+} filter_dummy_t;
+
+static int gui(filter_t *filter)
+{
+    filter_dummy_t *dummy = (void*)filter;
+    gui_text_wrapped("Just a test of a filter that does nothing.");
+    gui_input_int("X", &dummy->x, 0, 0);
+    return 0;
+}
+
+FILTER_REGISTER(dummy, filter_dummy_t,
+    .name = "Dummy",
+    .gui_fn = gui,
+)

src/goxel.h

@@ -33,6 +33,7 @@
 #include "assets.h"
 #include "block_def.h"
 #include "camera.h"
+#include "filters.h"
 #include "gesture.h"
 #include "gesture3d.h"
 #include "gui.h"
@@ -534,6 +535,7 @@ typedef struct goxel
         int current_panel; // Index of the current visible control panel.
         float panel_width;
         float viewport[4];
+        filter_t *current_filter;
     } gui;
 
     char **recent_files; // stb arraw of most recently used files.

src/gui/app.c

@@ -123,6 +123,7 @@ void gui_app(void)
     const float spacing = 8;
     int flags;
     int i;
+    filter_t *filter;
 
     goxel.show_export_viewport = false;
 
@@ -178,6 +179,18 @@ void gui_app(void)
         gui_window_end();
     }
 
+    filter = goxel.gui.current_filter;
+    if (filter) {
+        // XXX: we should have a way to center the filter window.
+        gui_window_begin(filter->name, 100, 100, goxel.gui.panel_width, 0,
+                         GUI_WINDOW_MOVABLE);
+        if (gui_panel_header(filter->name)) {
+            goxel.gui.current_filter = NULL;
+        }
+        filter->gui_fn(filter);
+        gui_window_end();
+    }
+
     goxel.pathtrace = goxel.pathtracer.status &&
         (goxel.gui.current_panel == PANEL_RENDER ||
          PANELS[PANEL_RENDER].detached);

src/gui/menu.c

@@ -71,6 +71,16 @@ static void on_script(void *user, const char *name)
         script_execute(name);
 }
 
+static void on_filter(void *user, const filter_t *filter)
+{
+    const action_t *action;
+    if (gui_menu_item(0, filter->name, true)) {
+        action = action_get_by_name(filter->action_id);
+        assert(action);
+        action_exec(action);
+    }
+}
+
 void gui_menu(void)
 {
     camera_t *cam;
@@ -151,6 +161,10 @@ void gui_menu(void)
         gui_menu_item(ACTION_view_default, _(RESET), true);
         gui_menu_end();
     }
+    if (gui_menu_begin("Filters", true)) { // Note: to translate.
+        filters_iter_all(NULL, on_filter);
+        gui_menu_end();
+    }
     if (gui_menu_begin("Scripts", true)) {
         if (gui_menu_item(0, "About Scripts", true))
             gui_open_popup("Scripts", 0, NULL, gui_about_scripts_popup);