Merge pull request #3 from pappersverk/issue-2-vertical-lines

Fix aritmetic error on vertical lines using line/5
pappersverk · Mar 4, 2020 · 62a6782 · 62a6782
2 parents f065581 + 5cda2f7
commit 62a6782
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Showing 2 changed files with 51 additions and 7 deletions.
diff --git a/lib/oled/display/impl/ssd_1306/draw.ex b/lib/oled/display/impl/ssd_1306/draw.ex
@@ -62,13 +62,16 @@ defmodule OLED.Display.Impl.SSD1306.Draw do
         {x1, y1, x2, y2}
       end
 
-    dx = x2 - x1
-    dy = y2 - y1
+    cond do
+      x1 == x2 ->
+        line_v(state, x1, y1, y2 - y1 + 1, opts)
 
-    Enum.reduce(x1..x2, state, fn x, acc ->
-      y = trunc(y1 + dy * (x - x1) / dx)
-      put_pixel(acc, x, y, opts)
-    end)
+      y1 == y2 ->
+        line_h(state, x1, y1, x2 - x1 + 1, opts)
+
+      true ->
+        do_line(state, x1, y1, x2, y2, opts)
+    end
   end
 
   def line_h(state, _x, _y, width, _opts) when width < 1,
@@ -132,4 +135,14 @@ defmodule OLED.Display.Impl.SSD1306.Draw do
 
   defp draw_circle(_x0, _y0, _x, _y, _f, _ddF_x, _ddF_y, _opts, state),
     do: state
+
+  defp do_line(state, x1, y1, x2, y2, opts) do
+    dx = x2 - x1
+    dy = y2 - y1
+
+    Enum.reduce(x1..x2, state, fn x, acc ->
+      y = trunc(y1 + dy * (x - x1) / dx)
+      put_pixel(acc, x, y, opts)
+    end)
+  end
 end
diff --git a/test/oled/display/impl/ssd_1306/line_test.exs b/test/oled/display/impl/ssd_1306/line_test.exs
@@ -39,7 +39,6 @@ defmodule OLED.Display.Impl.SSD1306.LineTest do
            ]
   end
 
-  #|> Enum.each(&IO.inspect/1)
   test "draw xor" do
     assert build_state(@w, @h)
            |> Draw.line(0, 0, 32, 8, [])
@@ -71,6 +70,38 @@ defmodule OLED.Display.Impl.SSD1306.LineTest do
            ]
   end
 
+  test "draw horizontal rect" do
+    assert build_state(@w, @h)
+           |> Draw.line(4, 5, 16, 5, [])
+           |> ascii_render() ==
+             [
+               "                                ",
+               "                                ",
+               "                                ",
+               "                                ",
+               "                                ",
+               "    #############               ",
+               "                                ",
+               "                                "
+             ]
+  end
+
+  test "draw vertical rect" do
+    assert build_state(@w, @h)
+           |> Draw.line(10, 1, 10, 6, [])
+           |> ascii_render() ==
+             [
+               "                                ",
+               "          #                     ",
+               "          #                     ",
+               "          #                     ",
+               "          #                     ",
+               "          #                     ",
+               "          #                     ",
+               "                                "
+             ]
+  end
+
   test "draw rect out 2" do
     assert build_state(@w, @h)
            |> Draw.line(-32, -8, 32, 8, [])