Optimized region drawing and fixed incorrect region clipping (#240)

Made small optimizations to Texture's SetRegion, SetLinearRegion,
GetRegion and Clear. They might not be super effective depending on how
the compiler already optimized them. The optimizations mainly focus on
removing the multiplication when transforming a position to an index by
using the row index rather than the y coordinate during iteration.
Also fixed regions not drawing properly when clipping against the sides
of a window and made GetRegion reject any region that isn't fully inside
of the window (previously accepted regions that clipped outside of the
right and bottom side, possibly leading to incorrect reads on the user
end due to desynchronized region dimensions)

Author: DaemonicGh

runtime/Sources/Renderer/Image.cpp

@@ -226,49 +226,60 @@ namespace mlx
 	void Texture::SetRegion(int x, int y, int w, int h, mlx_color* pixels) noexcept
 	{
 		MLX_PROFILE_FUNCTION();
-		if(x < 0 || y < 0 || static_cast<std::uint32_t>(x) >= m_width || static_cast<std::uint32_t>(y) >= m_height)
-			return;
-		if(w < 0 || h < 0)
+		if(w < 0 || h < 0 || x < -w || y < -h
+			|| x >= static_cast<int>(m_width) || y >= static_cast<int>(m_height))
 			return;
 		if(!m_staging_buffer.has_value())
 			OpenCPUBuffer();
-		for(std::uint32_t i = 0, moving_x = x, moving_y = y;; i++, moving_x++)
+		const int
+			start_x = std::max<int>(x, 0),
+			start_y = std::max<int>(y, 0),
+			start_row = start_y * m_width,
+			start_i = (start_y - y) * w + (start_x - x),
+			end_x = std::min<int>(x + w, m_width),
+			end_y = std::min<int>(y + h, m_height),
+			end_row = end_y * m_width,
+			incr = (x + w) - end_x + (start_x - x);
+		for(int i = start_i, dx = start_x, row = start_row;; i++, dx++)
 		{
-			if(moving_x >= static_cast<std::uint32_t>(x + w) || moving_x >= m_width)
+			if(dx >= end_x)
 			{
-				moving_x = x;
-				moving_y++;
-				if(moving_y >= static_cast<std::uint32_t>(y + h) || moving_y >= m_height)
+				i += incr;
+				dx = start_x;
+				row += m_width;
+				if(row >= end_row)
 					break;
 			}
 			if constexpr(std::endian::native == std::endian::little)
-				m_staging_buffer->GetMap<mlx_color*>()[(moving_y * m_width) + moving_x] = ReverseColor(pixels[i]);
+				m_staging_buffer->GetMap<mlx_color*>()[row + dx] = ReverseColor(pixels[i]);
 			else
-				m_staging_buffer->GetMap<mlx_color*>()[(moving_y * m_width) + moving_x] = pixels[i];
+				m_staging_buffer->GetMap<mlx_color*>()[row + dx] = pixels[i];
 		}
 		m_has_been_modified = true;
 	}
 
 	void Texture::SetLinearRegion(int x, int y, std::size_t len, mlx_color* pixels) noexcept
 	{
 		MLX_PROFILE_FUNCTION();
-		if(x < 0 || y < 0 || static_cast<std::uint32_t>(x) >= m_width || static_cast<std::uint32_t>(y) >= m_height)
+		if(x >= static_cast<int>(m_width) || y >= static_cast<int>(m_height))
 			return;
 		if(!m_staging_buffer.has_value())
 			OpenCPUBuffer();
+		int
+			start = y * m_width + x,
+			dest_start = std::max<int>(start, 0),
+			src_start = dest_start - start,
+			dest_end = std::min<int>(start + len, m_width * m_height);
 		if constexpr(std::endian::native == std::endian::little)
 		{
-			for(std::size_t i = 0; i < len && (y * m_width) + x + i < m_width * m_height; i++)
-				m_staging_buffer->GetMap<mlx_color*>()[(y * m_width) + x + i] = ReverseColor(pixels[i]);
+			for(int i = dest_start, j = src_start; i < dest_end; i++, j++)
+				m_staging_buffer->GetMap<mlx_color*>()[i] = ReverseColor(pixels[j]);
 		}
 		else
 		{
-			std::size_t len_guard;
-			if((y * m_width + x + len) < m_width * m_height)
-				len_guard = len;
-			else
-				len_guard = len - (m_width * m_height - (y * m_width + x + len));
-			std::memcpy(&m_staging_buffer->GetMap<mlx_color*>()[(y * m_width) + x], pixels, len_guard);
+			std::memcpy(
+				&m_staging_buffer->GetMap<mlx_color*>()[dest_start],
+				&pixels[src_start], dest_end - dest_start);
 		}
 		m_has_been_modified = true;
 	}
@@ -289,23 +300,23 @@ namespace mlx
 	void Texture::GetRegion(int x, int y, int w, int h, mlx_color* dst) noexcept
 	{
 		MLX_PROFILE_FUNCTION();
-		if(x < 0 || y < 0 || static_cast<std::uint32_t>(x) >= m_width || static_cast<std::uint32_t>(y) >= m_height)
+		if(w < 0 || h < 0 || x < 0 || y < 0 || static_cast<std::uint32_t>(x + w) >= m_width || static_cast<std::uint32_t>(y + h) >= m_height)
 			return;
 		if(!m_staging_buffer.has_value())
 			OpenCPUBuffer();
-		for(std::uint32_t i = 0, moving_x = x, moving_y = y;; i++, moving_x++)
+		for(std::uint32_t i = 0, dx = x, row = y * m_width;; i++, dx++)
 		{
-			if(moving_x >= static_cast<std::uint32_t>(x + w) || moving_x >= m_width)
+			if(dx >= m_width)
 			{
-				moving_x = x;
-				moving_y++;
-				if(moving_y >= static_cast<std::uint32_t>(y + h) || moving_y >= m_height)
+				dx = x;
+				row += m_width;
+				if(row >= m_height * m_width)
 					break;
 			}
 			if constexpr(std::endian::native == std::endian::little)
-				dst[i] = ReverseColor(m_staging_buffer->GetMap<mlx_color*>()[(moving_y * m_width) + moving_x]);
+				dst[i] = ReverseColor(m_staging_buffer->GetMap<mlx_color*>()[row + dx]);
 			else
-				dst[i] = m_staging_buffer->GetMap<mlx_color*>()[(moving_y * m_width) + moving_x];
+				dst[i] = m_staging_buffer->GetMap<mlx_color*>()[row + dx];
 		}
 	}
 
@@ -320,16 +331,8 @@ namespace mlx
 			processed_color.g = static_cast<std::uint8_t>(color.g * 255.f);
 			processed_color.b = static_cast<std::uint8_t>(color.b * 255.f);
 			processed_color.a = static_cast<std::uint8_t>(color.a * 255.f);
-			if(processed_color.r == 0 && processed_color.g == 0 && processed_color.b == 0)
-				std::memset(m_staging_buffer->GetMap(), processed_color.a, m_staging_buffer->GetSize());
-			else
-			{
-				for(std::size_t y = 0; y < m_height; y++)
-				{
-					for(std::size_t x = 0; x < m_width; x++)
-						m_staging_buffer->GetMap<mlx_color*>()[y * m_width + x] = processed_color;
-				}
-			}
+			for(std::size_t i = 0; i < m_width * m_height; i++)
+				m_staging_buffer->GetMap<mlx_color*>()[i] = processed_color;
 		}
 	}