[PATCH v8 36/44] kernel-shark: Add getStreamColorTable()

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

This method provides a hash table that maps the stream Ids to
rainbow-like colors.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 src/KsPlotTools.cpp | 50 +++++++++++++++++++++++++++++++++++++++++++++
 src/KsPlotTools.hpp |  4 ++++
 2 files changed, 54 insertions(+)

diff --git a/src/KsPlotTools.cpp b/src/KsPlotTools.cpp
index 113a6c0..400a3e2 100644
--- a/src/KsPlotTools.cpp
+++ b/src/KsPlotTools.cpp
@@ -97,6 +97,23 @@ void Color::setRainbowColor(int n)
 	set(r, g, b);
 }
 
+/** Alpha blending with white background. */
+void Color::blend(float alpha)
+{
+	if (alpha < 0 || alpha > 1.)
+		return;
+
+	auto lamBld = [alpha](int val) {
+		return  val * alpha + (1 - alpha) * 255;
+	};
+
+	int r = lamBld(this->r());
+	int g = lamBld(this->g());
+	int b = lamBld(this->b());
+
+	set(r, g, b);
+}
+
 /**
  * @brief Create a Hash table of Rainbow colors. The sorted Pid values are
  *	  mapped to the palette of Rainbow colors.
@@ -182,6 +199,39 @@ ColorTable getCPUColorTable()
 	return colors;
 }
 
+/**
+ * @brief Create a Hash table of Rainbow colors. The Steam Ids are
+ *	  mapped to the palette of Rainbow colors.
+ *
+ * @returns ColorTable instance.
+ */
+ColorTable getStreamColorTable()
+{
+	kshark_context *kshark_ctx(nullptr);
+	ColorTable colors;
+	Color color;
+	float alpha(.35);
+	int *streamIds;
+
+	if (!kshark_instance(&kshark_ctx))
+		return colors;
+
+	streamIds = kshark_all_streams(kshark_ctx);
+	for (int i = 0; i < kshark_ctx->n_streams; ++i) {
+		/*
+		 * Starting from index 6 provides better functioning of the
+		 * color scheme slider.
+		 */
+		color.setRainbowColor(i + 6);
+		color.blend(alpha);
+		colors[streamIds[i]] = color;
+	}
+
+	free(streamIds);
+
+	return colors;
+}
+
 /**
  * @brief Search the Hash table of Rainbow colors for a particular key (pid).
  *
diff --git a/src/KsPlotTools.hpp b/src/KsPlotTools.hpp
index 6e66373..dd6c77f 100644
--- a/src/KsPlotTools.hpp
+++ b/src/KsPlotTools.hpp
@@ -47,6 +47,8 @@ public:
 
 	void setRainbowColor(int n);
 
+	void blend(float alpha);
+
 	/**
 	 * @brief Get the C struct defining the RGB color.
 	 */
@@ -78,6 +80,8 @@ ColorTable getTaskColorTable();
 
 ColorTable getCPUColorTable();
 
+ColorTable getStreamColorTable();
+
 Color getColor(ColorTable *colors, int pid);
 
 /** Represents an abstract graphical element. */
-- 
2.25.1