commit 9bab3bd1c669b99cc1cd8d9f7a4571a6efab53de
Author: Stephen M. Cameron <stephenmcameron@gmail.com>
Date:   Mon Aug 30 13:53:02 2021 -0400

    Debug draw_vertex_buffer_2d
    
    Signed-off-by: Stephen M. Cameron <stephenmcameron@gmail.com>

diff --git a/graph_dev_opengl.c b/graph_dev_opengl.c
index 33c8263..c669ef7 100644
--- a/graph_dev_opengl.c
+++ b/graph_dev_opengl.c
@@ -1170,22 +1170,30 @@ void graph_dev_setup_colors(void *gtk_widget, void *gdk_color_huex, int nhuex)
 
 static void draw_vertex_buffer_2d()
 {
+	fprintf(stderr, "1 draw_vertex_buffer_2d()\n"); fflush(stderr);
 	if (sgc.nvertex_2d > 0) {
 		/* printf("start draw_vertex_buffer_2d %d\n", sgc.nvertex_2d); */
 		enable_2d_viewport();
+	fprintf(stderr, "2 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		/* transfer into opengl buffer */
 		glBindBuffer(GL_ARRAY_BUFFER, sgc.vertex_buffer_2d);
+	fprintf(stderr, "3 draw_vertex_buffer_2d()\n"); fflush(stderr);
 		glBufferSubData(GL_ARRAY_BUFFER, 0, sgc.nvertex_2d * sizeof(struct vertex_color_buffer_data),
 			sgc.vertex_data_2d);
+	fprintf(stderr, "4 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		glUseProgram(vertex_color_shader.program_id);
+	fprintf(stderr, "5 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		glUniformMatrix4fv(vertex_color_shader.mvp_matrix_id, 1, GL_FALSE, &sgc.ortho_2d_mvp.m[0][0]);
+	fprintf(stderr, "6 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		/* load x,y vertex position */
 		glEnableVertexAttribArray(vertex_color_shader.vertex_position_id);
+	fprintf(stderr, "7 draw_vertex_buffer_2d()\n"); fflush(stderr);
 		glBindBuffer(GL_ARRAY_BUFFER, sgc.vertex_buffer_2d);
+	fprintf(stderr, "8 draw_vertex_buffer_2d()\n"); fflush(stderr);
 		glVertexAttribPointer(
 			vertex_color_shader.vertex_position_id,
 			2,
@@ -1194,10 +1202,13 @@ static void draw_vertex_buffer_2d()
 			sizeof(struct vertex_color_buffer_data),
 			(void *)offsetof(struct vertex_color_buffer_data, position[0])
 		);
+	fprintf(stderr, "9 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		/* load the color as as 4 bytes and let opengl normalize them to 0-1 floats */
 		glEnableVertexAttribArray(vertex_color_shader.vertex_color_id);
+	fprintf(stderr, "10 draw_vertex_buffer_2d()\n"); fflush(stderr);
 		glBindBuffer(GL_ARRAY_BUFFER, sgc.vertex_buffer_2d);
+	fprintf(stderr, "11 draw_vertex_buffer_2d()\n"); fflush(stderr);
 		glVertexAttribPointer(
 			vertex_color_shader.vertex_color_id,
 			4,
@@ -1206,6 +1217,7 @@ static void draw_vertex_buffer_2d()
 			sizeof(struct vertex_color_buffer_data),
 			(void *)offsetof(struct vertex_color_buffer_data, color[0])
 		);
+	fprintf(stderr, "12 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		int i;
 		GLint start = 0;
@@ -1233,6 +1245,7 @@ static void draw_vertex_buffer_2d()
 				}
 			}
 		}
+	fprintf(stderr, "13 draw_vertex_buffer_2d()\n"); fflush(stderr);
 		if (start < sgc.nvertex_2d) {
 			GLsizei count = sgc.nvertex_2d - start;
 
@@ -1242,16 +1255,19 @@ static void draw_vertex_buffer_2d()
 			glDrawArrays(mode, start, count);
 			/* printf("glDrawArrays 2 mode=%d start=%d count=%d\n", mode, start, i - start); */
 		}
+	fprintf(stderr, "14 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		sgc.nvertex_2d = 0;
 
 		glDisableVertexAttribArray(vertex_color_shader.vertex_position_id);
 		glDisableVertexAttribArray(vertex_color_shader.vertex_color_id);
 		glUseProgram(0);
+	fprintf(stderr, "15 draw_vertex_buffer_2d()\n"); fflush(stderr);
 
 		/* orphan this buffer so we don't get blocked on these draw commands */
 		glBindBuffer(GL_ARRAY_BUFFER, sgc.vertex_buffer_2d);
 		glBufferData(GL_ARRAY_BUFFER, VERTEX_BUFFER_2D_SIZE, 0, GL_STREAM_DRAW);
+	fprintf(stderr, "16 draw_vertex_buffer_2d()\n"); fflush(stderr);
 	}
 }