constraints for text. added rotation constraint and rotate around center of elements

cudoku.c

@@ -58,7 +58,7 @@ void draw_win() {
   /* set_width_constraint(&constraints, window.width, UI_CONSTRAINT_FIXED); */
   /* set_height_constraint(&constraints, window.height, UI_CONSTRAINT_FIXED); */
 
-  Alignment align = ALIGN_TOP_RIGHT;
+  Alignment align = ALIGN_CENTER;
   int font_size = 72.0f;
 
   Sizef text_size = calculate_text_size(win_text, font_size);
@@ -67,12 +67,13 @@ void draw_win() {
   set_y_constraint(&constraints, 0, UI_CONSTRAINT_FIXED);
   set_width_constraint(&constraints, text_size.width, UI_CONSTRAINT_FIXED);
   set_height_constraint(&constraints, text_size.height, UI_CONSTRAINT_FIXED);
+  set_rotation_constraint(&constraints, get_time() * 50.f);
 
-  UIConstraints circle_const;
-  set_x_constraint(&circle_const, 50, UI_CONSTRAINT_FIXED);
-  set_y_constraint(&circle_const, 0, UI_CONSTRAINT_FIXED);
-  set_width_constraint(&circle_const, 70, UI_CONSTRAINT_FIXED);
-  set_height_constraint(&circle_const, 90, UI_CONSTRAINT_FIXED);
+  /* UIConstraints circle_const; */
+  /* set_x_constraint(&circle_const, 50, UI_CONSTRAINT_FIXED); */
+  /* set_y_constraint(&circle_const, 0, UI_CONSTRAINT_FIXED); */
+  /* set_width_constraint(&circle_const, 70, UI_CONSTRAINT_FIXED); */
+  /* set_height_constraint(&circle_const, 90, UI_CONSTRAINT_FIXED); */
 
 /*   draw_circle(circle_const, NULL, ALIGN_LEFT_CENTER); */
   draw_quad(constraints, &bg_color, 0.0, align);
@@ -84,7 +85,9 @@ void draw_win() {
 
   /* draw_triangle(constraints, &bg_color, ALIGN_CENTER); */
 
-  draw_text(win_text, font_size, (Vec2f){0.0, 0.0}, &text_color, align);
+  set_width_constraint(&constraints, 1, UI_CONSTRAINT_FIXED);
+  set_height_constraint(&constraints, 1, UI_CONSTRAINT_FIXED);
+  draw_text(win_text, font_size, constraints, &text_color, align);
 }
 
 void set_scale_factor(int width, int height, float *x, float *y) {

helper.c

@@ -28,17 +28,33 @@ void mult_4x4(Matrix4x4 *multiplicant, Matrix4x4 *multiplier) {
   *multiplicant = result;
 }
 
-// TODO: rotate around the center of the element
-// currently we rotate around the 0, 0 point of the element
+void apply_scale(Matrix4x4 *matrix, Sizef scale) {
+  Matrix4x4 temp = identity();
+
+  temp.m[0][0] = scale.width;
+  temp.m[1][1] = scale.height;
+
+  mult_4x4(matrix, &temp);
+}
+
 void apply_rotation(Matrix4x4 *model, float angle) {
-  Matrix4x4 ident = identity();
+  Matrix4x4 temp = identity();
 
-  ident.m[0][0] = cos(angle);
-  ident.m[0][1] = sin(angle);
-  ident.m[1][0] = -sin(angle);
-  ident.m[1][1] = cos(angle);
+  temp.m[0][0] = cos(angle);
+  temp.m[0][1] = sin(angle);
+  temp.m[1][0] = -sin(angle);
+  temp.m[1][1] = cos(angle);
 
-  mult_4x4(model, &ident);
+  mult_4x4(model, &temp);
+}
+
+void apply_translation(Matrix4x4 *matrix, Vec2f pos) {
+  Matrix4x4 temp = identity();
+
+  temp.m[3][0] = pos.x;
+  temp.m[3][1] = pos.y;
+
+  mult_4x4(matrix, &temp);
 }
 
 Matrix4x4 orthographic_projection_2d(float left, float right, float bottom, float top) {

helper.h

@@ -1,12 +1,12 @@
 #pragma once
 
-typedef struct {
-    float m[4][4];
-} Matrix4x4;
+#include "z_math.h"
 
 Matrix4x4 identity();
 void mult_4x4(Matrix4x4 *multiplicant, Matrix4x4 *multiplier);
+void apply_scale(Matrix4x4 *matrix, Sizef scale);
 void apply_rotation(Matrix4x4 *model, float angle);
+void apply_translation(Matrix4x4 *matrix, Vec2f pos);
 Matrix4x4 orthographic_projection_2d(float left, float right, float bottom, float top);
 int max(int a, int b);
 float maxf(float a, float b);

ui.c

@@ -314,6 +314,10 @@ void set_height_constraint(UIConstraints *constraints, float value, UIConstraint
   }
 }
 
+void set_rotation_constraint(UIConstraints *constraints, float angle_d) {
+  constraints->rotation = angle_d;
+}
+
 void apply_constraints(UIConstraints constraints, Vec2f *pos, Sizef *size) {
   *pos = (Vec2f){constraints.x, constraints.y};
   *size = (Sizef){constraints.width, constraints.height};
@@ -381,9 +385,11 @@ void draw_quad(UIConstraints constraints, Color *color, float border_radius, Ali
   apply_alignment(align, &pos, size);
 
   Matrix4x4 model = identity();
-  apply_rotation(&model, to_radians(0));
-  model.m[3][0] = pos.x;
-  model.m[3][1] = pos.y;
+  apply_translation(&model, (Vec2f){-size.width / 2.f, -size.height / 2.f});
+  apply_rotation(&model, to_radians(constraints.rotation));
+  apply_translation(&model, (Vec2f){size.width / 2.f, size.height / 2.f});
+
+  apply_translation(&model, pos);
 
   set_mat4f(font_shader, "model", (float *)model.m);
 
@@ -438,9 +444,11 @@ void draw_triangle(UIConstraints constraints, Color *color, Alignment align) {
   apply_alignment(align, &pos, size);
 
   Matrix4x4 model = identity();
-  apply_rotation(&model, to_radians(0));
-  model.m[3][0] = pos.x;
-  model.m[3][1] = pos.y;
+  apply_translation(&model, (Vec2f){-size.width / 2.f, -size.height / 2.f});
+  apply_rotation(&model, to_radians(constraints.rotation));
+  apply_translation(&model, (Vec2f){size.width / 2.f, size.height / 2.f});
+
+  apply_translation(&model, pos);
 
   set_mat4f(font_shader, "model", (float *)model.m);
 
@@ -461,7 +469,7 @@ void draw_triangle(UIConstraints constraints, Color *color, Alignment align) {
   glBindVertexArray(0);
 }
 
-void draw_text(const char* text, int font_size, Vec2f pos, Color *color, Alignment alignment) {
+void draw_text(const char* text, int font_size, UIConstraints constraints, Color *color, Alignment alignment) {
   use_shader(font_shader);
   if (color) {
     set_vec4f(font_shader, "textColor", color->r / 255.f, color->g / 255.f, color->b / 255.f, color->a / 255.f);
@@ -470,17 +478,24 @@ void draw_text(const char* text, int font_size, Vec2f pos, Color *color, Alignme
   }
   set_mat4f(font_shader, "projection", (float *)zephr_context.projection.m);
 
+  Vec2f pos = { 0.f, 0.f };
+  Sizef size = {0};
+
+  apply_constraints(constraints, &pos, &size);
+
   Sizef text_size = calculate_text_size(text, FONT_PIXEL_SIZE);
-  float font_scale = (float)font_size / FONT_PIXEL_SIZE;
+  float font_scale = (float)font_size / FONT_PIXEL_SIZE * size.width;
 
   apply_alignment(alignment, &pos, (Sizef){ text_size.width * font_scale, text_size.height * font_scale });
 
   Matrix4x4 model = identity();
-  model.m[0][0] = font_scale;
-  model.m[1][1] = font_scale;
-  apply_rotation(&model, to_radians(0));
-  model.m[3][0] = pos.x;
-  model.m[3][1] = pos.y;
+  apply_scale(&model, (Sizef){font_scale, font_scale});
+
+  apply_translation(&model, (Vec2f){-text_size.width * font_scale / 2.f, -text_size.height * font_scale / 2.f});
+  apply_rotation(&model, to_radians(constraints.rotation));
+  apply_translation(&model, (Vec2f){text_size.width *font_scale / 2.f, text_size.height * font_scale / 2.f});
+
+  apply_translation(&model, pos);
 
   set_mat4f(font_shader, "model", (float *)model.m);
 
@@ -495,6 +510,10 @@ void draw_text(const char* text, int font_size, Vec2f pos, Color *color, Alignme
   glActiveTexture(GL_TEXTURE0);
   glBindVertexArray(font_vao);
 
+  // we use the original text and character sizes in the loop and then we just
+  // scale up or down the model matrix to get the desired font size.
+  // this way everything works out fine and we get to transform the text using the
+  // model matrix
   int c = 0;
   int x = 0;
   while (text[c] != '\0') {

ui.h

@@ -2,34 +2,7 @@
 
 #include <stdbool.h>
 
-#include "helper.h"
-
-typedef struct Size {
-  int width;
-  int height;
-} Size;
-
-typedef struct Sizef {
-  float width;
-  float height;
-} Sizef;
-
-typedef struct Vec2 {
-  int x;
-  int y;
-} Vec2;
-
-typedef struct Vec2f {
-  float x;
-  float y;
-} Vec2f;
-
-typedef struct Color {
-  float r;
-  float g;
-  float b;
-  float a;
-} Color;
+#include "z_math.h"
 
 typedef struct Character {
   unsigned int texture_id;
@@ -70,6 +43,7 @@ typedef struct UIConstraints {
   float y;
   float width;
   float height;
+  float rotation;
 } UIConstraints;
 
 int init_zephr(const char* font_path, const char* window_title, Size window_size, Color *clear_color);
@@ -81,8 +55,9 @@ void set_x_constraint(UIConstraints *constraints, float value, UIConstraint type
 void set_y_constraint(UIConstraints *constraints, float value, UIConstraint type);
 void set_width_constraint(UIConstraints *constraints, float value, UIConstraint type);
 void set_height_constraint(UIConstraints *constraints, float value, UIConstraint type);
+void set_rotation_constraint(UIConstraints *constraints, float angle_d);
 void draw_quad(UIConstraints constraints, Color *color, float border_radius, Alignment align);
 void draw_circle(UIConstraints constraints, Color *color, Alignment align);
 void draw_triangle(UIConstraints constraints, Color *color, Alignment align);
-void draw_text(const char* text, int font_size, Vec2f pos, Color *color, Alignment align);
+void draw_text(const char* text, int font_size, UIConstraints constraints, Color *color, Alignment align);
 Sizef calculate_text_size(const char *text, int font_size);

z_math.h

@@ -0,0 +1,32 @@
+#pragma once
+
+typedef struct {
+    float m[4][4];
+} Matrix4x4;
+
+typedef struct Size {
+  int width;
+  int height;
+} Size;
+
+typedef struct Sizef {
+  float width;
+  float height;
+} Sizef;
+
+typedef struct Vec2 {
+  int x;
+  int y;
+} Vec2;
+
+typedef struct Vec2f {
+  float x;
+  float y;
+} Vec2f;
+
+typedef struct Color {
+  float r;
+  float g;
+  float b;
+  float a;
+} Color;