Removed unnecessary else and added guard clauses

As the title says, I've removed some unnecessary "else return" statements, and added some guard clauses so we don't have to go another level of indentation in the code.

olcPixelGameEngine.h

@@ -194,7 +194,7 @@
 
 	Author
 	~~~~~~
-	David Barr, aka javidx9, ©OneLoneCoder 2018, 2019, 2020, 2021
+	David Barr, aka javidx9, ©OneLoneCoder 2018, 2019, 2020, 2021
 */
 #pragma endregion
 
@@ -1306,13 +1306,9 @@ namespace olc
 		{
 			if (x >= 0 && x < width && y >= 0 && y < height)
 				return pColData[y * width + x];
-			else
+			return Pixel(0, 0, 0, 0);
-				return Pixel(0, 0, 0, 0);
-		}
-		else
-		{
-			return pColData[abs(y % height) * width + abs(x % width)];
 		}
+		return pColData[abs(y % height) * width + abs(x % width)];
 	}
 
 	bool Sprite::SetPixel(int32_t x, int32_t y, Pixel p)
@@ -1322,8 +1318,7 @@ namespace olc
 			pColData[y * width + x] = p;
 			return true;
 		}
-		else
+		return false;
-			return false;
 	}
 
 	Pixel Sprite::Sample(float x, float y) const
@@ -1438,12 +1433,9 @@ namespace olc
 			pDecal = std::make_unique<olc::Decal>(pSprite.get(), filter, clamp);
 			return olc::rcode::OK;
 		}
-		else
+		pSprite.release();
-		{
+		pSprite = nullptr;
-			pSprite.release();
+		return olc::rcode::NO_FILE;
-			pSprite = nullptr;
-			return olc::rcode::NO_FILE;
-		}
 	}
 
 	olc::Decal* Renderable::Decal() const
@@ -1764,16 +1756,14 @@ namespace olc
 	{
 		if (pDrawTarget)
 			return pDrawTarget->width;
-		else
+		return 0;
-			return 0;
 	}
 
 	int32_t PixelGameEngine::GetDrawTargetHeight() const
 	{
 		if (pDrawTarget)
 			return pDrawTarget->height;
-		else
+		return 0;
-			return 0;
 	}
 
 	uint32_t PixelGameEngine::GetFPS() const
@@ -1830,9 +1820,7 @@ namespace olc
 		if (!pDrawTarget) return false;
 
 		if (nPixelMode == Pixel::NORMAL)
-		{
 			return pDrawTarget->SetPixel(x, y, p);
-		}
 
 		if (nPixelMode == Pixel::MASK)
 		{
@@ -1852,9 +1840,7 @@ namespace olc
 		}
 
 		if (nPixelMode == Pixel::CUSTOM)
-		{
 			return pDrawTarget->SetPixel(x, y, funcPixelMode(x, y, p, pDrawTarget->GetPixel(x, y)));
-		}
 
 		return false;
 	}
@@ -1952,33 +1938,34 @@ namespace olc
 
 		if (radius > 0)
 		{
-			int x0 = 0;
+			Draw(x, y, p);
-			int y0 = radius;
+			return;
-			int d = 3 - 2 * radius;
+		}
 
-			while (y0 >= x0) // only formulate 1/8 of circle
+		int x0 = 0;
-			{
+		int y0 = radius;
-				// Draw even octants
+		int d = 3 - 2 * radius;
-				if (mask & 0x01) Draw(x + x0, y - y0, p);// Q6 - upper right right
-				if (mask & 0x04) Draw(x + y0, y + x0, p);// Q4 - lower lower right
-				if (mask & 0x10) Draw(x - x0, y + y0, p);// Q2 - lower left left
-				if (mask & 0x40) Draw(x - y0, y - x0, p);// Q0 - upper upper left
-				if (x0 != 0 && x0 != y0)
-				{
-					if (mask & 0x02) Draw(x + y0, y - x0, p);// Q7 - upper upper right
-					if (mask & 0x08) Draw(x + x0, y + y0, p);// Q5 - lower right right
-					if (mask & 0x20) Draw(x - y0, y + x0, p);// Q3 - lower lower left
-					if (mask & 0x80) Draw(x - x0, y - y0, p);// Q1 - upper left left
-				}
 
-				if (d < 0)
+		while (y0 >= x0) // only formulate 1/8 of circle
-					d += 4 * x0++ + 6;
+		{
-				else
+			// Draw even octants
-					d += 4 * (x0++ - y0--) + 10;
+			if (mask & 0x01) Draw(x + x0, y - y0, p);// Q6 - upper right right
+			if (mask & 0x04) Draw(x + y0, y + x0, p);// Q4 - lower lower right
+			if (mask & 0x10) Draw(x - x0, y + y0, p);// Q2 - lower left left
+			if (mask & 0x40) Draw(x - y0, y - x0, p);// Q0 - upper upper left
+			if (x0 != 0 && x0 != y0)
+			{
+				if (mask & 0x02) Draw(x + y0, y - x0, p);// Q7 - upper upper right
+				if (mask & 0x08) Draw(x + x0, y + y0, p);// Q5 - lower right right
+				if (mask & 0x20) Draw(x - y0, y + x0, p);// Q3 - lower lower left
+				if (mask & 0x80) Draw(x - x0, y - y0, p);// Q1 - upper left left
 			}
+
+			if (d < 0)
+				d += 4 * x0++ + 6;
+			else
+				d += 4 * (x0++ - y0--) + 10;
 		}
-		else
-			Draw(x, y, p);
 	}
 
 	void PixelGameEngine::FillCircle(const olc::vi2d& pos, int32_t radius, Pixel p)
@@ -1991,36 +1978,37 @@ namespace olc
 
 		if (radius > 0)
 		{
-			int x0 = 0;
+			Draw(x, y, p);
-			int y0 = radius;
+			return;
-			int d = 3 - 2 * radius;
+		}
 
-			auto drawline = [&](int sx, int ex, int y)
+		int x0 = 0;
-			{
+		int y0 = radius;
-				for (int x = sx; x <= ex; x++)
+		int d = 3 - 2 * radius;
-					Draw(x, y, p);
-			};
 
-			while (y0 >= x0)
+		auto drawline = [&](int sx, int ex, int y)
-			{
+		{
-				drawline(x - y0, x + y0, y - x0);
+			for (int x = sx; x <= ex; x++)
-				if (x0 > 0)	drawline(x - y0, x + y0, y + x0);
+				Draw(x, y, p);
+		};
 
-				if (d < 0)
+		while (y0 >= x0)
-					d += 4 * x0++ + 6;
+		{
-				else
+			drawline(x - y0, x + y0, y - x0);
+			if (x0 > 0)	drawline(x - y0, x + y0, y + x0);
+
+			if (d < 0)
+				d += 4 * x0++ + 6;
+			else
+			{
+				if (x0 != y0)
 				{
-					if (x0 != y0)
+					drawline(x - x0, x + x0, y - y0);
-					{
+					drawline(x - x0, x + x0, y + y0);
-						drawline(x - x0, x + x0, y - y0);
-						drawline(x - x0, x + x0, y + y0);
-					}
-					d += 4 * (x0++ - y0--) + 10;
 				}
+				d += 4 * (x0++ - y0--) + 10;
 			}
 		}
-		else
-			Draw(x, y, p);
 	}
 
 	void PixelGameEngine::DrawRect(const olc::vi2d& pos, const olc::vi2d& size, Pixel p)
@@ -2552,22 +2540,22 @@ namespace olc
 		di.uv = { { 0.0f, 0.0f}, {0.0f, 1.0f}, {1.0f, 1.0f}, {1.0f, 0.0f} };
 		olc::vf2d center;
 		float rd = ((pos[2].x - pos[0].x) * (pos[3].y - pos[1].y) - (pos[3].x - pos[1].x) * (pos[2].y - pos[0].y));
-		if (rd != 0)
+
+		if (rd == 0) return;
+
+		rd = 1.0f / rd;
+		float rn = ((pos[3].x - pos[1].x) * (pos[0].y - pos[1].y) - (pos[3].y - pos[1].y) * (pos[0].x - pos[1].x)) * rd;
+		float sn = ((pos[2].x - pos[0].x) * (pos[0].y - pos[1].y) - (pos[2].y - pos[0].y) * (pos[0].x - pos[1].x)) * rd;
+		if (!(rn < 0.f || rn > 1.f || sn < 0.f || sn > 1.f)) center = pos[0] + rn * (pos[2] - pos[0]);
+		float d[4];	for (int i = 0; i < 4; i++)	d[i] = (pos[i] - center).mag();
+		for (int i = 0; i < 4; i++)
 		{
-			rd = 1.0f / rd;
+			float q = d[i] == 0.0f ? 1.0f : (d[i] + d[(i + 2) & 3]) / d[(i + 2) & 3];
-			float rn = ((pos[3].x - pos[1].x) * (pos[0].y - pos[1].y) - (pos[3].y - pos[1].y) * (pos[0].x - pos[1].x)) * rd;
+			di.uv[i] *= q; di.w[i] *= q;
-			float sn = ((pos[2].x - pos[0].x) * (pos[0].y - pos[1].y) - (pos[2].y - pos[0].y) * (pos[0].x - pos[1].x)) * rd;
+			di.pos[i] = { (pos[i].x * vInvScreenSize.x) * 2.0f - 1.0f, ((pos[i].y * vInvScreenSize.y) * 2.0f - 1.0f) * -1.0f };
-			if (!(rn < 0.f || rn > 1.f || sn < 0.f || sn > 1.f)) center = pos[0] + rn * (pos[2] - pos[0]);
-			float d[4];	for (int i = 0; i < 4; i++)	d[i] = (pos[i] - center).mag();
-			for (int i = 0; i < 4; i++)
-			{
-				float q = d[i] == 0.0f ? 1.0f : (d[i] + d[(i + 2) & 3]) / d[(i + 2) & 3];
-				di.uv[i] *= q; di.w[i] *= q;
-				di.pos[i] = { (pos[i].x * vInvScreenSize.x) * 2.0f - 1.0f, ((pos[i].y * vInvScreenSize.y) * 2.0f - 1.0f) * -1.0f };
-			}
-			di.mode = nDecalMode;
-			vLayers[nTargetLayer].vecDecalInstance.push_back(di);
 		}
+		di.mode = nDecalMode;
+		vLayers[nTargetLayer].vecDecalInstance.push_back(di);
 	}
 
 	void PixelGameEngine::DrawWarpedDecal(olc::Decal* decal, const std::array<olc::vf2d, 4>& pos, const olc::Pixel& tint)