1 files changed, 116 insertions, 0 deletions

diff --git a/src/ui/visbuf.c b/src/ui/visbuf.c
new file mode 100644
index 00000000..82346ff0
--- /dev/null
+++ b/src/ui/visbuf.c
@@ -0,0 +1,116 @@
+#include "visbuf.h"
+#include "window.h"
+#include "util.h"
+
+iDefineTypeConstruction(VisBuf)
+
+void init_VisBuf(iVisBuf *d) {
+    d->texSize = zero_I2();
+    iZap(d->buffers);
+}
+
+void deinit_VisBuf(iVisBuf *d) {
+    dealloc_VisBuf(d);
+}
+
+void invalidate_VisBuf(iVisBuf *d) {
+    iForIndices(i, d->buffers) {
+        iZap(d->buffers[i].validRange);
+    }
+}
+
+void alloc_VisBuf(iVisBuf *d, const iInt2 size, int granularity) {
+    const iInt2 texSize = init_I2(size.x, (size.y / 2 / granularity + 1) * granularity);
+    if (!d->buffers[0].texture || !isEqual_I2(texSize, d->texSize)) {
+        d->texSize = texSize;
+        iForIndices(i, d->buffers) {
+            iVisBufTexture *tex = &d->buffers[i];
+            if (tex->texture) {
+                SDL_DestroyTexture(tex->texture);
+            }
+            tex->texture =
+                SDL_CreateTexture(renderer_Window(get_Window()),
+                                  SDL_PIXELFORMAT_RGBA8888,
+                                  SDL_TEXTUREACCESS_STATIC | SDL_TEXTUREACCESS_TARGET,
+                                  texSize.x,
+                                  texSize.y);
+            SDL_SetTextureBlendMode(tex->texture, SDL_BLENDMODE_NONE);
+            tex->origin = i * texSize.y;
+            iZap(tex->validRange);
+        }
+    }
+}
+
+void dealloc_VisBuf(iVisBuf *d) {
+    d->texSize = zero_I2();
+    iForIndices(i, d->buffers) {
+        SDL_DestroyTexture(d->buffers[i].texture);
+        d->buffers[i].texture = NULL;
+    }
+}
+
+void reposition_VisBuf(iVisBuf *d, const iRangei vis) {
+    d->vis = vis;
+    iRangei good = { 0, 0 };
+    size_t avail[3], numAvail = 0;
+    /* Check which buffers are available for reuse. */ {
+        iForIndices(i, d->buffers) {
+            iVisBufTexture *buf = d->buffers + i;
+            const iRangei region = { buf->origin, buf->origin + d->texSize.y };
+            if (region.start >= vis.end || region.end <= vis.start) {
+                avail[numAvail++] = i;
+                iZap(buf->validRange);
+            }
+            else {
+                good = union_Rangei(good, region);
+            }
+        }
+    }
+    if (numAvail == iElemCount(d->buffers)) {
+        /* All buffers are outside the visible range, do a reset. */
+        d->buffers[0].origin = vis.start;
+        d->buffers[1].origin = vis.start + d->texSize.y;
+        d->buffers[2].origin = vis.start + 2 * d->texSize.y;
+    }
+    else {
+        /* Extend to cover the visible range. */
+        while (vis.start < good.start) {
+            iAssert(numAvail > 0);
+            d->buffers[avail[--numAvail]].origin = good.start - d->texSize.y;
+            good.start -= d->texSize.y;
+        }
+        while (vis.end > good.end) {
+            iAssert(numAvail > 0);
+            d->buffers[avail[--numAvail]].origin = good.end;
+            good.end += d->texSize.y;
+        }
+    }
+}
+
+void invalidRanges_VisBuf(const iVisBuf *d, const iRangei full, iRangei *out_invalidRanges) {
+    iForIndices(i, d->buffers) {
+        const iVisBufTexture *buf = d->buffers + i;
+        const iRangei before = { full.start, buf->validRange.start };
+        const iRangei after  = { buf->validRange.end, full.end };
+        const iRangei region = intersect_Rangei(d->vis, (iRangei){ buf->origin,
+                                                                   buf->origin + d->texSize.y });
+        out_invalidRanges[i] = intersect_Rangei(before, region);
+        if (isEmpty_Rangei(out_invalidRanges[i])) {
+            out_invalidRanges[i] = intersect_Rangei(after, region);
+        }
+    }
+}
+
+void draw_VisBuf(const iVisBuf *d, iInt2 topLeft) {
+    SDL_Renderer *render = renderer_Window(get_Window());
+    iForIndices(i, d->buffers) {
+        const iVisBufTexture *buf = d->buffers + i;
+        SDL_RenderCopy(render,
+                       buf->texture,
+                       NULL,
+                       &(SDL_Rect){ topLeft.x,
+                                    topLeft.y + buf->origin,
+                                    d->texSize.x,
+                                    d->texSize.y });
+    }
+}