From dca4f283ccb08fa4c4e0b3fb47c3a5b703b1d319 Mon Sep 17 00:00:00 2001
From: MihailRis <mexaruc@gmail.com>
Date: Fri, 7 Mar 2025 20:15:59 +0300
Subject: [PATCH] add canvas:clear(...), canvas:line(...)

---
 .../lua/usertypes/lua_type_canvas.cpp         | 147 +++++++++++++++---
 1 file changed, 129 insertions(+), 18 deletions(-)

diff --git a/src/logic/scripting/lua/usertypes/lua_type_canvas.cpp b/src/logic/scripting/lua/usertypes/lua_type_canvas.cpp
index acba361d..ad79f0ca 100644
--- a/src/logic/scripting/lua/usertypes/lua_type_canvas.cpp
+++ b/src/logic/scripting/lua/usertypes/lua_type_canvas.cpp
@@ -17,6 +17,7 @@ union RGBA {
     struct {
         uint8_t r, g, b, a;
     };
+    uint8_t arr[4];
     uint32_t rgba;
 };
 
@@ -49,32 +50,140 @@ static int l_at(State* L) {
     return 0;
 }
 
+static RGBA get_rgba(State* L, int first) {
+    RGBA rgba {};
+    rgba.a = 255;
+    switch (gettop(L) - first) {
+        case 0:
+            rgba.rgba = static_cast<uint>(tointeger(L, first));
+            break;
+        case 3:
+            rgba.a = static_cast<ubyte>(tointeger(L, first + 3));
+            [[fallthrough]];
+        case 2:
+            rgba.r = static_cast<ubyte>(tointeger(L, first));
+            rgba.g = static_cast<ubyte>(tointeger(L, first + 1));
+            rgba.b = static_cast<ubyte>(tointeger(L, first + 2));
+            break;
+    }
+    return rgba;
+}
+
 static int l_set(State* L) {
     auto x = static_cast<uint>(tointeger(L, 2));
     auto y = static_cast<uint>(tointeger(L, 3));
 
     if (auto pixel = get_at(L, x, y)) {
-        switch (gettop(L)) {
-            case 4:
-                pixel->rgba = static_cast<uint>(tointeger(L, 4));
-                return 1;
-            case 6:
-                pixel->r = static_cast<ubyte>(tointeger(L, 4));
-                pixel->g = static_cast<ubyte>(tointeger(L, 5));
-                pixel->b = static_cast<ubyte>(tointeger(L, 6));
-                pixel->a = 255;
-                return 1;
-            case 7:
-                pixel->r = static_cast<ubyte>(tointeger(L, 4));
-                pixel->g = static_cast<ubyte>(tointeger(L, 5));
-                pixel->b = static_cast<ubyte>(tointeger(L, 6));
-                pixel->a = static_cast<ubyte>(tointeger(L, 7));
-                return 1;
-            default:
-                return 0;
+        *pixel = get_rgba(L, 4);
+    }
+    return 0;
+}
+
+static int l_clear(State* L) {
+    RGBA rgba {};
+    if (gettop(L) > 1) {
+        rgba = get_rgba(L, 2);
+    }
+    if (auto canvas = touserdata<LuaCanvas>(L, 1)) {
+        auto& image = canvas->data();
+        ubyte* data = image.getData();
+        size_t pixels = image.getWidth() * image.getHeight();
+        const size_t channels = 4;
+        for (size_t i = 0; i < pixels * channels; i++) {
+            data[i] = rgba.arr[i % channels];
         }
     }
+    return 0;
+}
 
+bool clip_line(int& x1, int& y1, int& x2, int& y2, int width, int height) {
+    const int left = 0;
+    const int right = width;
+    const int bottom = 0;
+    const int top = height;
+
+    int dx = x2 - x1;
+    int dy = y2 - y1;
+
+    float t0 = 0.0f;
+    float t1 = 1.0f;
+
+    auto clip = [](int p, int q, float& t0, float& t1) {
+        if (p == 0) {
+            return q >= 0;
+        }
+        float t = static_cast<float>(q) / p;
+        if (p < 0) {
+            if (t > t1) return false;
+            if (t > t0) t0 = t;
+        } else {
+            if (t < t0) return false;
+            if (t < t1) t1 = t;
+        }
+        return true;
+    };
+
+    if (!clip(-dx, x1 - left, t0, t1)) return false;
+    if (!clip( dx, right - x1, t0, t1)) return false;
+    if (!clip(-dy, y1 - bottom, t0, t1)) return false;
+    if (!clip( dy, top - y1, t0, t1)) return false;
+
+    if (t1 < 1.0f) {
+        x2 = x1 + static_cast<int>(std::round(t1 * dx));
+        y2 = y1 + static_cast<int>(std::round(t1 * dy));
+    }
+    if (t0 > 0.0f) {
+        x1 = x1 + static_cast<int>(std::round(t0 * dx));
+        y1 = y1 + static_cast<int>(std::round(t0 * dy));
+    }
+    return true;
+}
+
+static int l_line(State* L) {
+    int x1 = tointeger(L, 2);
+    int y1 = tointeger(L, 3);
+
+    int x2 = tointeger(L, 4);
+    int y2 = tointeger(L, 5);
+
+    RGBA rgba = get_rgba(L, 6);
+    if (auto canvas = touserdata<LuaCanvas>(L, 1)) {
+        auto& image = canvas->data();
+        ubyte* data = image.getData();
+        uint width = image.getWidth();
+        uint height = image.getHeight();
+        const uint channels = 4;
+
+        if ((x1 < 0 || x1 >= width || x2 < 0 || x2 >= width ||
+            y1 < 0 || y1 >= height || y2 < 0 || y2 >= height) &&
+            !clip_line(x1, y1, x2, y2, width, height)) {
+            return 0;
+        }
+        
+        int dx = glm::abs(x2 - x1);
+        int dy = -glm::abs(y2 - y1);
+        int sx = x1 < x2 ? 1 : -1;
+        int sy = y1 < y2 ? 1 : -1;
+        int err = dx + dy;
+    
+        while (true) {
+            size_t pos = (y1 * width + x1) * channels;
+            for (int i = 0; i < channels; i++) {
+                data[pos + i] = rgba.arr[i];
+            }
+            if (x1 == x2 && y1 == y2) break;
+            
+            int e2 = 2 * err;
+            if (e2 >= dy) {
+                err += dy;
+                x1 += sx;
+            }
+            if (e2 <= dx) {
+                err += dx;
+                y1 += sy;
+            }
+        }
+    }
     return 0;
 }
 
@@ -88,6 +197,8 @@ static int l_update(State* L) {
 static std::unordered_map<std::string, lua_CFunction> methods {
     {"at", lua::wrap<l_at>},
     {"set", lua::wrap<l_set>},
+    {"clear", lua::wrap<l_clear>},
+    {"line", lua::wrap<l_line>},
     {"update", lua::wrap<l_update>}
 };