*: initial commit derived from whale stage code

This code was used in whale [1], and prior to that was used in
a smaller project called mal.  Since I seemed to be doing a lot of
reusing and building upon this, it seemed prudent to just stick it
in a repo as a .a I could submodule in future SDL2 art projects.

There are some kludges in this code currently, which will be fixed up
in time.

1 files changed, 453 insertions, 0 deletions

diff --git a/src/stage.c b/src/stage.c
new file mode 100644
index 0000000..20a1fc0
--- /dev/null
+++ b/src/stage.c
@@ -0,0 +1,453 @@
+/*
+ *  Copyright (C) 2018  Vito Caputo - <vcaputo@pengaru.com>
+ *
+ *  This program is free software: you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 3 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <SDL.h>
+
+#include "list.h"
+#include "stage.h"
+
+typedef struct v2f_t {
+	float	x, y;
+} v2f_t;
+
+typedef struct aabb_t {
+	v2f_t	min, max;
+} aabb_t;
+
+typedef struct stage_cached_t {
+	int		width, height;
+	SDL_Texture	*texture;
+} stage_cached_t;
+
+struct stage_node_t {
+	list_head_t		nodes;
+	char			name[STAGE_NODE_NAME_MAX];
+	stage_cached_t		cached;
+	aabb_t			aabb;		/* node coordinates expressed in the space of -1.0...1.0 */
+	float			alpha;		/* alpha for the texture when composited */
+	double			angle;		/* angle for the texture when composited */
+	unsigned		active:1;	/* node is active */
+	unsigned		locked:1;	/* node is locked */
+
+	stage_render_func_t	render;		/* render object into a texture */
+	stage_free_func_t	free;		/* free object */
+	void			*object;	/* object */
+};
+
+struct stage_t {
+	list_head_t	layers[STAGE_LAYERS_MAX];
+	SDL_Renderer	*renderer;		/* target renderer */
+	float		aspect_ratio;		/* width/height ratio of stage, -1.0...1.0 range of node coordinates map to this ratio. */
+};
+
+
+/* minimally initialize a node to carry an object */
+static void node_init(stage_node_t *node, const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
+{
+	strncpy(node->name, name, sizeof(node->name));
+	node->render = render_func;
+	node->free = free_func;
+	node->object = object;
+}
+
+
+/* allocate a node, no list manipulation occurs, this purely creates a node in isolation and assigns its associated name, object and functions */
+static stage_node_t * node_new(const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
+{
+	stage_node_t	*node;
+
+	node = calloc(1, sizeof(stage_node_t));
+	if (!node)
+		return NULL;
+
+	node_init(node, name, object, render_func, free_func);
+
+	return node;
+}
+
+
+/* free a node, no list manipulation occurs, this is purely cleanup of the node and its associated texture and object */
+static void node_free(stage_node_t *node)
+{
+	if (node->free)
+		node->free(node->object);
+	if (node->cached.texture)
+		SDL_DestroyTexture(node->cached.texture);
+	free(node);
+}
+
+
+/* returns a new node installed at the specified layer */
+stage_node_t * stage_node_new(stage_t *stage, int layer, const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
+{
+	stage_node_t	*node;
+
+	node = node_new(name, object, render_func, free_func);
+	if (!node)
+		return NULL;
+
+	list_add_tail(&node->nodes, &stage->layers[layer]);
+
+	return node;
+}
+
+
+/* replace a given node's object only - retain render/free hooks and everything else, invalidates cache  - DOES NOT FREE OLD OBJECT */
+/* FIXME: this is being used as a kludge to swap frames in an svg - 
+ * eliminate this bullshit and add support for animations or at least frames,
+ * the stage really shouldn't have anything to do with it, we can dick with
+ * the svg behind its back.  I just don't currently have the helpers for creating
+ * svg nodes actually giving out the bare svg handle currently, so the stage_node_t
+ * is all I have to dick with at the moment.  Next time!  This really dicks with
+ * the resource lifecycle - if the stage frees the node, which object was active
+ * at the time and which object still needs to be freed because it wasn't in
+ * the stage when the node was killed?  It's totally shitty, and I'm aware.
+ */
+void stage_node_set_object(const stage_t *stage, stage_node_t *node, void *object)
+{
+	if (node->cached.texture) {
+		SDL_DestroyTexture(node->cached.texture);
+		node->cached.texture = NULL;
+	}
+
+	node->object = object;
+}
+
+/* FIXME: GROSS fuck me */
+void stage_node_get_object(const stage_t *stage, stage_node_t *node, void **res_object)
+{
+	*res_object = node->object;
+}
+
+
+/* replaces a given node's object-related properties but otherwise keeping the existing state */
+void stage_node_replace(const stage_t *stage, stage_node_t *node, const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
+{
+	if (node->free)
+		node->free(node->object);
+
+	if (node->cached.texture) {
+		SDL_DestroyTexture(node->cached.texture);
+		node->cached.texture = NULL;
+	}
+
+	node_init(node, name, object, render_func, free_func);
+}
+
+
+/* frees a given node removing it from the stage */
+stage_node_t * stage_node_free(stage_t *stage, stage_node_t *node)
+{
+	if (node) {
+		list_del(&node->nodes);
+		node_free(node);
+	}
+
+	return NULL;
+}
+
+
+/* set the alpha on a node */
+void stage_node_set_alpha(const stage_t *stage, stage_node_t *node, float alpha)
+{
+	/* TODO: this should probably mark something dirty for when we stop always recomposing everything */
+	node->alpha = alpha;
+}
+
+
+/* set the aabb for a node */
+void stage_node_set_aabb(const stage_t *stage, stage_node_t *node, const aabb_t *aabb)
+{
+	node->aabb = *aabb;
+}
+
+
+/* get the aabb for a node */
+void stage_node_get_aabb(const stage_t *stage, stage_node_t *node, aabb_t *res_aabb)
+{
+	*res_aabb = node->aabb;
+}
+
+
+/* set a node to active (participates in rendering) */
+void stage_node_set_active(const stage_t *stage, stage_node_t *node)
+{
+	node->active = 1;
+}
+
+
+/* set a node to inactive (doesn't participate in rendering) */
+void stage_node_set_inactive(const stage_t *stage, stage_node_t *node)
+{
+	/* TODO: should this discard the potentially cached texture? */
+	node->active = 0;
+}
+
+
+/* set a node to locked (doesn't get freed by clears) */
+void stage_node_set_locked(const stage_t *stage, stage_node_t *node)
+{
+	node->locked = 1;
+}
+
+
+/* set a node to unlocked (default, gets freed by clears) */
+void stage_node_set_unlocked(const stage_t *stage, stage_node_t *node)
+{
+	node->locked = 0;
+}
+
+
+/* set a node's layer */
+void stage_node_set_layer(stage_t *stage, stage_node_t *node, int layer)
+{
+	/* TODO: assert layer sanity */
+	list_del(&node->nodes);
+	list_add_tail(&node->nodes, &stage->layers[layer]);
+}
+
+
+void stage_node_set_angle(const stage_t *stage, stage_node_t *node, double angle)
+{
+	node->angle = angle;
+}
+
+
+void stage_node_get_angle(const stage_t *stage, stage_node_t *node, double *res_angle)
+{
+	*res_angle = node->angle;
+}
+
+
+/* create a new stage with the given aspect ratio */
+stage_t * stage_new(SDL_Renderer *renderer, float aspect_ratio)
+{
+	stage_t	*stage;
+	int	i;
+
+	stage = calloc(1, sizeof(stage_t));
+	if (!stage)
+		return NULL;
+
+	for (i = 0; i < STAGE_LAYERS_MAX; i++)
+		INIT_LIST_HEAD(&stage->layers[i]);
+
+	stage->renderer = renderer;
+	stage->aspect_ratio = aspect_ratio;
+
+	return stage;
+}
+
+static void _stage_clear(stage_t *stage, int force)
+{
+	stage_node_t	*node, *_node;
+	int		i;
+
+	for (i = 0; i < STAGE_LAYERS_MAX; i++) {
+		list_for_each_entry_safe(node, _node, &stage->layers[i], nodes) {
+			if (force || !node->locked)
+				stage_node_free(stage, node);
+		}
+	}
+}
+
+/* free everything in the stage, but keep the stage around */
+/* probably good hygiene to clear everything when there's no intention of
+ * reusing nodes at the start of a new context, in case something is left
+ * around unintentionally. */
+void stage_clear(stage_t *stage)
+{
+	_stage_clear(stage, 0);
+}
+
+
+/* free the supplied stage and all associated textures and objects */
+stage_t * stage_free(stage_t *stage)
+{
+
+	if (stage) {
+		_stage_clear(stage, 1);
+		free(stage);
+	}
+
+	return NULL;
+}
+
+
+/* fit a stage to the supplied dimensions, returns the fitted dimensions in the result pointers */
+/* the idea is this can be used in a window resize hook to enforce the stage's aspect ratio */
+void stage_fit(const stage_t *stage, int width, int height, int *res_width, int *res_height)
+{
+	float	full_width = stage->aspect_ratio * ((float)height);
+
+	if (full_width == width) {
+		/* perfect fit */
+		*res_width = width;
+		*res_height = height;
+	} else if (full_width > width) {
+		/* height is too large */
+		*res_height = (1.0f / stage->aspect_ratio) * ((float)width);
+		*res_width = width;
+	} else {
+		/* width is too large */
+		*res_width = full_width;
+		*res_height = height;
+	}
+}
+
+
+static void aabb_to_rect(const aabb_t *aabb, const SDL_Rect *stage_rect, SDL_Rect *res_rect)
+{
+	float	half_w = ((float)stage_rect->w) * .5f, half_h = ((float)stage_rect->h) * .5f;	/* FIXME silly to recompute this repeatedly... */
+
+	res_rect->x = stage_rect->x;
+	res_rect->y = stage_rect->y;
+	res_rect->x += ((float)aabb->min.x) * half_w + half_w;
+	res_rect->y += stage_rect->h - (((float)aabb->max.y) * half_h + half_h);
+
+	res_rect->w = (aabb->max.x - aabb->min.x) * half_w;
+	res_rect->h = (aabb->max.y - aabb->min.y) * half_h;
+}
+
+
+static void render_nodes(list_head_t *head, SDL_Renderer *renderer, SDL_Rect *dest_rect)
+{
+	stage_node_t	*node;
+
+	list_for_each_entry(node, head, nodes) {
+		SDL_Rect	node_rect;
+
+		if (!node->active)
+			continue;
+
+		/* scale the node's aabb stage coordinates to destination renderer coordinates */
+		aabb_to_rect(&node->aabb, dest_rect, &node_rect);
+
+		/* if we have a cached texture, see if the dimensions changed */
+		if (node->cached.texture &&
+		    (node_rect.w != node->cached.width ||
+		     node_rect.h != node->cached.height)) {
+			SDL_DestroyTexture(node->cached.texture);
+			node->cached.texture = NULL;
+		}
+
+		/* Tell the node to draw its cached texture */
+		/* The draw function may either use the existing texture when non-NULL or destroy and create a new one,
+		 * whatever is most convenient for it.
+		 * If the texture is NULL, a create & render must be performed, and 1 returned.
+		 * If the texture is non-NULL, and there's no animation or anything to be done, 0 may simply be returned.
+		 * Otherwise, if supplied a non-NULL texture and it's modified, 1 must be returned.
+		 */
+		/* XXX: at this time, the return value is ignored (it always composites the stage even when unchanged) */
+		node->render(renderer, node->object, node_rect.w, node_rect.h, &node->cached.texture);
+		node->cached.width = node_rect.w;
+		node->cached.height = node_rect.h;
+		SDL_SetTextureAlphaMod(node->cached.texture, ((float)node->alpha * 255.0f));
+
+		/* copy the texture to renderer */
+		if (node->angle == 0)
+			SDL_RenderCopy(renderer, node->cached.texture, NULL, &node_rect);
+		else
+			SDL_RenderCopyEx(renderer, node->cached.texture, NULL, &node_rect, node->angle, NULL, SDL_FLIP_NONE);
+	}
+}
+
+
+/* XXX: ANOTHER KLUDGE FIXME */
+/* we shouldn't need to let this out of the stage, but for the mouse aiming
+ * it was easier this way for now.
+ */
+void stage_get_output_size(stage_t *stage, int *res_width, int *res_height)
+{
+	SDL_GetRendererOutputSize(stage->renderer, res_width, res_height);
+}
+
+
+/* render the supplied stage into the supplied renderer */
+/* the aspect_ratio of the stage will be enforced in filling the logical size
+ * of the renderer.  Unless the aspect ratio matches precisely, stage_render()
+ * will center the rendering and leave blank borders on the edges left empty.
+ * The renderer may be sized precisely by first calling stage_fit().
+ */
+void stage_render(stage_t *stage)
+{
+	SDL_Rect	rect;
+	int		i, width, height;
+
+	/* XXX TODO: investigate renderer viewports and scale factors */
+	SDL_GetRendererOutputSize(stage->renderer, &width, &height);
+
+	stage_fit(stage, width, height, &rect.w, &rect.h);
+	rect.x = (width - rect.w) / 2;
+	rect.y = (height - rect.h) / 2;
+
+	SDL_RenderClear(stage->renderer);	/* TODO: handle -1 on error */
+
+	for (i = 0; i < STAGE_LAYERS_MAX; i++)
+		render_nodes(&stage->layers[i], stage->renderer, &rect);
+}
+
+
+/* lookup a node from a name */
+stage_node_t * stage_node_lookup_name(const stage_t *stage, const char *name)
+{
+	stage_node_t	*node;
+	int		i;
+
+	for (i = 0; i < STAGE_LAYERS_MAX; i++) {
+		list_for_each_entry(node, &stage->layers[i], nodes) {
+			if (!strncmp(node->name, name, sizeof(node->name)))
+				return node;
+		}
+	}
+
+	return NULL;
+}
+
+
+/* lookup a node from a cartesian renderer coordinate */
+stage_node_t * stage_node_lookup_cartesian(const stage_t *stage, int x, int y)
+{
+	stage_node_t	*node;
+	SDL_Rect	rect;
+	int		i, width, height;
+
+	/* FIXME: copy-pasta with render, factor out */
+	SDL_GetRendererOutputSize(stage->renderer, &width, &height);
+
+	stage_fit(stage, width, height, &rect.w, &rect.h);
+	rect.x = (width - rect.w) / 2;
+	rect.y = (height - rect.h) / 2;
+
+	/* this is currently very simple: find the first top-most node
+	 * including the specified coordinate.
+	 */
+	for (i = STAGE_LAYERS_MAX - 1; i >= 0; i--) {
+		list_for_each_entry(node, &stage->layers[i], nodes) {
+			SDL_Rect	node_rect;
+
+			if (!node->active)
+				continue;
+
+			aabb_to_rect(&node->aabb, &rect, &node_rect);
+			if (x >= node_rect.x && x < node_rect.x + node_rect.w &&
+			    y >= node_rect.y && y < node_rect.y + node_rect.h)
+				return node;
+		}
+	}
+
+	return NULL;
+}