From cbd7effd3b0b8a3b19b127f7aad97c75bc680201 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 30 Mar 2020 16:59:45 +0200
Subject: [PATCH] LibGfx: Support vertical gradient fill (not just horizontal)
 :^)

---
 Libraries/LibGfx/Painter.cpp | 40 +++++++++++++++++++++++++++---------
 Libraries/LibGfx/Painter.h   |  1 +
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/Libraries/LibGfx/Painter.cpp b/Libraries/LibGfx/Painter.cpp
index 93e01de82b7..fc656eaae30 100644
--- a/Libraries/LibGfx/Painter.cpp
+++ b/Libraries/LibGfx/Painter.cpp
@@ -141,7 +141,7 @@ void Painter::fill_rect(const Rect& a_rect, Color color)
     }
 }
 
-void Painter::fill_rect_with_gradient(const Rect& a_rect, Color gradient_start, Color gradient_end)
+void Painter::fill_rect_with_gradient(Orientation orientation, const Rect& a_rect, Color gradient_start, Color gradient_end)
 {
 #ifdef NO_FPU
     return fill_rect(a_rect, gradient_start);
@@ -151,12 +151,12 @@ void Painter::fill_rect_with_gradient(const Rect& a_rect, Color gradient_start,
     if (clipped_rect.is_empty())
         return;
 
-    int x_offset = clipped_rect.x() - rect.x();
+    int offset = clipped_rect.primary_offset_for_orientation(orientation) - rect.primary_offset_for_orientation(orientation);
 
     RGBA32* dst = m_target->scanline(clipped_rect.top()) + clipped_rect.left();
     const size_t dst_skip = m_target->pitch() / sizeof(RGBA32);
 
-    float increment = (1.0 / ((rect.width()) / 255.0));
+    float increment = (1.0 / ((rect.primary_size_for_orientation(orientation)) / 255.0));
 
     int r2 = gradient_start.red();
     int g2 = gradient_start.green();
@@ -165,20 +165,40 @@ void Painter::fill_rect_with_gradient(const Rect& a_rect, Color gradient_start,
     int g1 = gradient_end.green();
     int b1 = gradient_end.blue();
 
-    for (int i = clipped_rect.height() - 1; i >= 0; --i) {
-        float c = x_offset * increment;
-        for (int j = 0; j < clipped_rect.width(); ++j) {
-            dst[j] = Color(
+    if (orientation == Orientation::Horizontal) {
+        for (int i = clipped_rect.height() - 1; i >= 0; --i) {
+            float c = offset * increment;
+            for (int j = 0; j < clipped_rect.width(); ++j) {
+                dst[j] = Color(
+                    r1 / 255.0 * c + r2 / 255.0 * (255 - c),
+                    g1 / 255.0 * c + g2 / 255.0 * (255 - c),
+                    b1 / 255.0 * c + b2 / 255.0 * (255 - c))
+                             .value();
+                c += increment;
+            }
+            dst += dst_skip;
+        }
+    } else {
+        float c = offset * increment;
+        for (int i = clipped_rect.height() - 1; i >= 0; --i) {
+            Color color(
                 r1 / 255.0 * c + r2 / 255.0 * (255 - c),
                 g1 / 255.0 * c + g2 / 255.0 * (255 - c),
-                b1 / 255.0 * c + b2 / 255.0 * (255 - c))
-                         .value();
+                b1 / 255.0 * c + b2 / 255.0 * (255 - c));
+            for (int j = 0; j < clipped_rect.width(); ++j) {
+                dst[j] = color.value();
+            }
             c += increment;
+            dst += dst_skip;
         }
-        dst += dst_skip;
     }
 }
 
+void Painter::fill_rect_with_gradient(const Rect& a_rect, Color gradient_start, Color gradient_end)
+{
+    return fill_rect_with_gradient(Orientation::Horizontal, a_rect, gradient_start, gradient_end);
+}
+
 void Painter::draw_ellipse_intersecting(const Rect& rect, Color color, int thickness)
 {
     constexpr int number_samples = 100; // FIXME: dynamically work out the number of samples based upon the rect size
diff --git a/Libraries/LibGfx/Painter.h b/Libraries/LibGfx/Painter.h
index efc2f64ab8a..ea12cdffde0 100644
--- a/Libraries/LibGfx/Painter.h
+++ b/Libraries/LibGfx/Painter.h
@@ -45,6 +45,7 @@ public:
     ~Painter();
     void clear_rect(const Rect&, Color);
     void fill_rect(const Rect&, Color);
+    void fill_rect_with_gradient(Orientation, const Rect&, Color gradient_start, Color gradient_end);
     void fill_rect_with_gradient(const Rect&, Color gradient_start, Color gradient_end);
     void draw_rect(const Rect&, Color, bool rough = false);
     void draw_bitmap(const Point&, const CharacterBitmap&, Color = Color());