/* mu_x11.c -- an Xlib/Xft backend for microui.
 *
 * microui is renderer-agnostic: it emits a command list of clipped
 * rectangles, text runs and icons, and asks the host two questions about
 * font metrics. This answers those and draws the commands into an
 * off-screen pixmap, then blits it, so a frame never appears half-drawn.
 *
 * SPDX-License-Identifier: MIT (matching the vendored microui)
 */
#define _POSIX_C_SOURCE 200809L
#include <X11/Xlib.h>
#include <X11/Xft/Xft.h>
#include <stdio.h>
#include <string.h>
#include "vendor/microui.h"
#include "mu_x11.h"

static Display *dpy;
static Window   win;
static Visual  *vis;
static Colormap cmap;
static XftFont *fnt;
static XftDraw *xd;
static Pixmap   buf;
static GC       gc;
static int      bw, bh;

int mux_text_width(mu_Font font, const char *s, int len)
{
	(void)font;
	XGlyphInfo gi;
	if (len < 0) len = strlen(s);
	XftTextExtentsUtf8(dpy, fnt, (const FcChar8 *)s, len, &gi);
	return gi.xOff;
}

int mux_text_height(mu_Font font)
{
	(void)font;
	return fnt->ascent + fnt->descent;
}

void mux_init(Display *d, Window w, const char *fontname)
{
	dpy = d; win = w;
	int scr = DefaultScreen(dpy);
	vis  = DefaultVisual(dpy, scr);
	cmap = DefaultColormap(dpy, scr);
	fnt  = XftFontOpenName(dpy, scr, fontname);
	gc   = XCreateGC(dpy, win, 0, NULL);
	buf = 0; xd = NULL; bw = bh = 0;
}

static void ensure_buffer(int w, int h)
{
	if (buf && w == bw && h == bh) return;
	if (xd)  { XftDrawDestroy(xd); xd = NULL; }
	if (buf) { XFreePixmap(dpy, buf); buf = 0; }
	buf = XCreatePixmap(dpy, win, w, h, DefaultDepth(dpy, DefaultScreen(dpy)));
	xd  = XftDrawCreate(dpy, buf, vis, cmap);
	bw = w; bh = h;
}

static void xft_of(mu_Color c, XftColor *out)
{
	XRenderColor rc = { c.r * 257, c.g * 257, c.b * 257, c.a * 257 };
	XftColorAllocValue(dpy, vis, cmap, &rc, out);
}

static const char *icon_glyph(int id)
{
	switch (id) {
	case MU_ICON_CLOSE:     return "x";
	case MU_ICON_CHECK:     return "*";
	case MU_ICON_COLLAPSED: return ">";
	case MU_ICON_EXPANDED:  return "v";
	default:                return "?";
	}
}

/* CLAMP BEFORE CONVERTING. XRectangle's w/h are unsigned SHORT, and microui
   resets its scissor by emitting an "unclipped" rect of 0x1000000 -- which
   truncates to 0 in 16 bits, turning "clip nothing" into "clip everything".
   The symptom is that a panel draws its first screenful and the rest
   silently vanishes, which reads as a layout or buffer bug and is neither. */
static void set_clip(mu_Rect r)
{
	int x = r.x, y = r.y, w = r.w, h = r.h;
	if (x < 0) { w += x; x = 0; }
	if (y < 0) { h += y; y = 0; }
	if (w > bw - x) w = bw - x;
	if (h > bh - y) h = bh - y;
	if (w <= 0 || h <= 0) { w = 0; h = 0; }
	XRectangle xr = { (short)x, (short)y, (unsigned short)w, (unsigned short)h };
	Region reg = XCreateRegion();
	XUnionRectWithRegion(&xr, reg, reg);
	XftDrawSetClip(xd, reg);
	XDestroyRegion(reg);
}

void mux_present(mu_Context *ctx, int w, int h, mu_Color bg)
{
	ensure_buffer(w, h);
	XftDrawSetClip(xd, NULL);

	XftColor col;
	xft_of(bg, &col);
	XftDrawRect(xd, &col, 0, 0, w, h);
	XftColorFree(dpy, vis, cmap, &col);

	mu_Command *cmd = NULL;
	while (mu_next_command(ctx, &cmd)) {
		switch (cmd->type) {
		case MU_COMMAND_RECT:
			xft_of(cmd->rect.color, &col);
			XftDrawRect(xd, &col, cmd->rect.rect.x, cmd->rect.rect.y,
			            cmd->rect.rect.w, cmd->rect.rect.h);
			XftColorFree(dpy, vis, cmap, &col);
			break;
		case MU_COMMAND_TEXT:
			xft_of(cmd->text.color, &col);
			XftDrawStringUtf8(xd, &col, fnt, cmd->text.pos.x,
			                  cmd->text.pos.y + fnt->ascent,
			                  (const FcChar8 *)cmd->text.str,
			                  strlen(cmd->text.str));
			XftColorFree(dpy, vis, cmap, &col);
			break;
		case MU_COMMAND_ICON: {
			const char *g = icon_glyph(cmd->icon.id);
			int tw = mux_text_width(NULL, g, 1);
			xft_of(cmd->icon.color, &col);
			XftDrawStringUtf8(xd, &col, fnt,
			                  cmd->icon.rect.x + (cmd->icon.rect.w - tw) / 2,
			                  cmd->icon.rect.y + fnt->ascent
			                    + (cmd->icon.rect.h - mux_text_height(NULL)) / 2,
			                  (const FcChar8 *)g, 1);
			XftColorFree(dpy, vis, cmap, &col);
			break;
		}
		case MU_COMMAND_CLIP:
			set_clip(cmd->clip.rect);
			break;
		}
	}
	XftDrawSetClip(xd, NULL);
	XCopyArea(dpy, buf, win, gc, 0, 0, w, h, 0, 0);
	XFlush(dpy);
}