From 0bf0a4a1eff69fc78f27635e006e07c849d5bff9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Mon, 3 Jul 2023 22:54:25 +0200
Subject: [PATCH] UIContext: Add an easy way to draw drop shadows under
 rectangular things

---
 Common/Math/geom2d.h   |  3 +++
 Common/UI/Context.cpp  | 11 +++++++++++
 Common/UI/Context.h    |  3 +++
 UI/OnScreenDisplay.cpp |  4 +---
 4 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/Common/Math/geom2d.h b/Common/Math/geom2d.h
index 3d2223c36e..f319d7c79d 100644
--- a/Common/Math/geom2d.h
+++ b/Common/Math/geom2d.h
@@ -69,6 +69,9 @@ struct Bounds {
 	Bounds Expand(float xAmount, float yAmount) const {
 		return Bounds(x - xAmount, y - yAmount, w + xAmount * 2, h + yAmount * 2);
 	}
+	Bounds Expand(float left, float top, float right, float bottom) const {
+		return Bounds(x - left, y - top, w + left + right, h + top + bottom);
+	}
 	Bounds Offset(float xAmount, float yAmount) const {
 		return Bounds(x + xAmount, y + yAmount, w, h);
 	}
diff --git a/Common/UI/Context.cpp b/Common/UI/Context.cpp
index cb62571bf0..6e4e277f07 100644
--- a/Common/UI/Context.cpp
+++ b/Common/UI/Context.cpp
@@ -313,6 +313,17 @@ void UIContext::FillRect(const UI::Drawable &drawable, const Bounds &bounds) {
 	} 
 }
 
+void UIContext::DrawRectDropShadow(const Bounds &bounds, float radius, float alpha, uint32_t color) {
+	if (alpha <= 0.0f)
+		return;
+
+	color = colorAlpha(color, alpha);
+
+	// Bias the shadow downwards a bit.
+	Bounds shadowBounds = bounds.Expand(radius, 0.5 * radius, radius, 1.5 * radius);
+	Draw()->DrawImage4Grid(theme->dropShadow4Grid, shadowBounds.x, shadowBounds.y, shadowBounds.x2(), shadowBounds.y2(), color, radius * (1.0f / 24.0f) * 2.0f);
+}
+
 void UIContext::DrawImageVGradient(ImageID image, uint32_t color1, uint32_t color2, const Bounds &bounds) {
 	uidrawbuffer_->DrawImageStretchVGradient(image, bounds.x, bounds.y, bounds.x2(), bounds.y2(), color1, color2);
 }
diff --git a/Common/UI/Context.h b/Common/UI/Context.h
index 1e2767d181..f8c409c287 100644
--- a/Common/UI/Context.h
+++ b/Common/UI/Context.h
@@ -77,6 +77,8 @@ public:
 
 	void SetTintSaturation(float tint, float sat);
 
+	// High level drawing functions. They generally assume the default texture to be bounds.
+
 	void SetFontStyle(const UI::FontStyle &style);
 	const UI::FontStyle &GetFontStyle() { return *fontStyle_; }
 	void SetFontScale(float scaleX, float scaleY);
@@ -88,6 +90,7 @@ public:
 	void DrawTextRect(const char *str, const Bounds &bounds, uint32_t color, int align = 0);
 	void DrawTextShadowRect(const char *str, const Bounds &bounds, uint32_t color, int align = 0);
 	void FillRect(const UI::Drawable &drawable, const Bounds &bounds);
+	void DrawRectDropShadow(const Bounds &bounds, float radius, float alpha, uint32_t color = 0);
 	void DrawImageVGradient(ImageID image, uint32_t color1, uint32_t color2, const Bounds &bounds);
 
 	// in dps, like dp_xres and dp_yres
diff --git a/UI/OnScreenDisplay.cpp b/UI/OnScreenDisplay.cpp
index 9d921b666f..51d633940d 100644
--- a/UI/OnScreenDisplay.cpp
+++ b/UI/OnScreenDisplay.cpp
@@ -99,9 +99,7 @@ static void RenderNotice(UIContext &dc, Bounds bounds, float height1, NoticeLeve
 
 	uint32_t foreGround = whiteAlpha(alpha);
 
-	Bounds shadowBounds = bounds.Expand(10.0f);
-
-	dc.Draw()->DrawImage4Grid(dc.theme->dropShadow4Grid, shadowBounds.x, shadowBounds.y + 4.0f, shadowBounds.x2(), shadowBounds.y2(), alphaMul(0xFF000000, 0.9f * alpha), 1.0f);
+	dc.DrawRectDropShadow(bounds, 12.0f, 0.7f * alpha);
 
 	dc.FillRect(background, bounds);