implement set_rotation and draw_line

assets/epaper.lua

@@ -1,6 +1,20 @@
 local paper = require('paper')
 paper.init()
+paper.clear()
+
 print(
   'width: ' .. paper.get_width(),
   'height: ' .. paper.get_height()
 )
+
+pad_w = paper.get_width() * 0.12
+pad_h = paper.get_height() * 0.12
+
+for i = 0, 15 do
+  for j = 1, 4 do
+    paper.draw_line(paper.get_height() / 16 * i, j, paper.get_width(), paper.get_height() - 4 + j, i * 16)
+  end
+  -- paper.draw_line(0, paper.get_height(), paper.get_width(), paper.get, i * 16)
+end
+
+paper.update()

main/paper.h

@@ -39,7 +39,29 @@ static int get_height (lua_State *L) {
     return 1;
 }
 
+static int set_rotation (lua_State *L) {
+    char *rotation = lua_tostring(L, -1);
+    luaL_argcheck(L, strcmp(rotation, "landscape") == 0 || strcmp(rotation, "portrait") == 0, -1, "expected `rotation` to be either 'landscape' or 'portrait'");
+    epd_set_rotation(strcmp(rotation, "landscape") == 0 ? EPD_ROT_LANDSCAPE : EPD_ROT_PORTRAIT);
+    return 0;
+}
+
 static int draw_line (lua_State *L) {
+    int x1, y1, x2, y2, color;
+    int isnum;
+
+    x1 = lua_tonumberx(L, -5, &isnum);
+    luaL_argcheck(L, isnum, -5, "expected `x1` to be a number");
+    y1 = lua_tonumberx(L, -4, &isnum);
+    luaL_argcheck(L, isnum, -4, "expected `y1` to be a number");
+    x2 = lua_tonumberx(L, -3, &isnum);
+    luaL_argcheck(L, isnum, -3, "expected `x2` to be a number");
+    y2 = lua_tonumberx(L, -2, &isnum);
+    luaL_argcheck(L, isnum, -2, "expected `y2` to be a number");
+    color = lua_tonumberx(L, -1, &isnum);
+    luaL_argcheck(L, isnum && color >= 0 && color < 256, -1, "expected `color` to be a number within [0, 255]");
+
+    epd_draw_line(x1, y1, x2, y2, color, fb);
     return 0;
 }
 
@@ -58,6 +80,7 @@ static const struct luaL_Reg paper[] = {
   {"get_width", get_width},
   {"get_height", get_height},
 
+  {"set_rotation", set_rotation},
   {"draw_line", draw_line},
   {"update", update},