commit e8fcc41e40dee07d062bff51636e464ff9d98215

Author: Hermet Park <hermet@hermet.pe.kr>
Date:   Mon Sep 12 16:50:00 2016 +0900

    evas map: fix the rendering problem.

    I got an issue report about map rendering.
    After investigated, I found that was introduced by data overflow.

    For fast computation, evas map uses integer data type rather than float,
    that gives up some range of data size.

    So, if vertex range is a little large but still reasonable,
    polygon won'be properly displayed due to the integer overflow.

    We can fix this by changing FPc data type to 64 bits (ie, long long)
    But I didn't do yet though I can simply fix this costlessly.

    By the way, my test case map points are below.

    0: -1715, -5499
    1: -83, -1011
    2: 1957, 5721
    3: 325, 1233

    and gl result is perfect but sw is totally broken.

    @fix

Change-Id: I04c1f61556c67553486588cc7a59c83b96371cd8

diff --git a/src/lib/evas/common/evas_map_image.c b/src/lib/evas/common/evas_map_image.c
index cec21f64801fe3ada312d66a9082c4e8ced3448e..bdf56aa2717963179f003220547ed9ef5c8bcdca 100644 (file)
--- a/src/lib/evas/common/evas_map_image.c
+++ b/src/lib/evas/common/evas_map_image.c
@@ -183,8 +183,15 @@ _calc_spans(RGBA_Map_Point *p, Line *spans, int ystart, int yend, int cx, int cy
              edge_h = (p[e2].y - p[e1].y) >> FP;  //edge height
              if (edge_h < 1) edge_h = 1;
              t = (((y << FP) + (FP1 / 2) - 1) - p[e1].y) >> FP;
-             x= p[e2].x - p[e1].x;  //edge width
-             x = p[e1].x + ((x * t) / edge_h); // intersected x point
+             x = p[e2].x - p[e1].x;  //edge width
+
+             FPc temp = (x * t);
+
+             // TODO: prevent data overflow. We can remove this exception if FPc type is more than integer.
+             if (temp < 0) temp = (((x >> FP) * t) / edge_h) << FP;
+             else temp /= edge_h;
+
+             x = p[e1].x + temp; // intersected x point
 
 /*             
              // FIXME: 3d accuracy here